diesel electric yacht propulsion

Propulsion Systems for Monohull

The silence of an Oceanvolt electric propulsion is a skipper's dream.  Whether quietly maneuvering through a harbor or motor-sailing on low-wind days to create your own apparent wind, our electric solutions will enhance and extend your sailing enjoyment. 

Oceanvolt offers Hybrid or Electric systems as a power & propulsion option in partnership with many leading monohull boat builders - adding new partners continuously. We also offer repowering solutions for converting away from legacy diesel engines – removing the diesel engine, fuel tanks and exhaust system - cleaning up greasy, smelly engine compartments and freeing up both weight and space below deck.

Oceanvolt systems are scaled and configured to achieve maximum efficiency - taking into consideration boat length, beam and displacement as well as system weight and placement within the boat.  Range, beyond battery capacity, is extended through hydro generation while sailing above 6kn.  This can be complemented with either a portable AC generator or a DC generator (in larger boats or for long distance cruising).

All Oceanvolt systems are engineered to operate at 48 volts for passenger safety and ease of repair. Oceanvolt systems are extremely low maintenance and do not require winterizing (no annual engine maintenance/storage costs).

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Diesel Electric Drive

• By Chuck Husick
• Updated: October 4, 2007

Siemens EcoProp

Your next yacht may be powered with a new, but at the same time old and extensively proven, power system-a diesel electric drive. First used in 1903 to propel the triple-screw Russian tanker Vandal on the Volga River and Caspian Sea, diesel electric propulsion is now used in the most modern cruise ships and in thousands of other commercial vessels. Although the idea of powering your yacht with the indirect, two-step diesel electric energy transfer system may appear to be unnecessarily complex, its many advantages can make it a compellingly attractive alternative to a conventional direct mechanical prop-shaft drive.

The benefits of diesel electric drive begin with the design freedom the system affords the yacht’s designer. The engine can be installed wherever appropriate to achieve optimum use of space for the accommodation. Noise and vibration are more easily suppressed than in a conventional direct engine-to-propeller drive. Turning the props with electric motors enhances slow-speed maneuverability by providing unrestricted minimum prop speeds with 100 percent torque available to provide immediate power response at all times. Prop synchronization is automatic and extremely precise. When under way all of the electrical power required by the vessel can be supplied from the diesel electric propulsion system, eliminating the need to run a genset. A diesel electric power system can drive multiple propellers from a single engine or use multiple engines to power one or more props. In a twin-engine/twin-prop system, one engine can power both props when operating within the speed limits imposed in many areas. Electrical power from the vessel’s genset can be used to propel the boat, providing a built-in backup-especially valuable for yachts with single-engine installations. Conversely, the propulsion system can serve as a backup for the yacht’s gensets.

The more than 100-year history of marine diesel electric systems began as a response to the impossibility of quickly reversing the direction of rotation of early direct-to-prop-shaft-coupled diesel engines. With a diesel-powered direct current (DC) generator and a DC motor connected to the prop shaft, the direction of prop rotation could be controlled by a switch. The 100 percent torque, zero-speed capability of the electric motor led to the overwhelming use of diesel electric power for railroad locomotives. Diesel electric drives found a natural application in submarines and many surface ships. Today’s cruise ships, where 70-80 percent of the total onboard power is required for the “hotel” side of the vessel, are diesel electric powered. The power demands can be enormous at times. A trivial example: 1,500,000 watts, equal to more than 1,400 hp, is needed to simultaneously power half of the 1,500-watt hair dryers on a 1,400-stateroom cruise ship.

While the equipment designed to serve the massive needs of cruise ships is unsuitable for any reasonable-sized yacht, numerous land-mobile applications including buses, very large trucks and the cranes used in container ports need power levels similar to those required by a yacht. These land-mobile applications require high overall efficiency, installation flexibility, virtually 100 percent torque at close to zero speed and must meet demanding reliability and durability standards. Fortunately, equipment designed and perfected for these uses is ideal for propelling many types of yachts.

From the helmsman’s standpoint the Siemens diesel electric propulsion system is totally transparent, functioning identically to a conventional power control system, with some welcome and useful advantages. In a twin-prop installation, two conventional-appearing single-lever electronic power controls send commands to the drive control system computer (DICO in Siemens’ terms). Digital messages from the DICO manage the diesel engine’s speed governor and control the current flow from the propulsion converters to the prop-drive motors. The power curve of the engine is programmed into the control computer and used to set engine rpm to the speed that provides the required power with optimum fuel efficiency. It is generally unnecessary for the helmsman to monitor engine rpm. Placing a prop control in neutral allows the prop to freewheel, with no risk of damaging the gearbox, a benefit when the vessel is propelled by the other prop. There are no restrictions on rapid movement of the control from ahead to astern. Moving both controls beyond a preselected prop shaft speed, usually about 400 rpm, will automatically and very precisely synchronize the propellers. In fact, the precision with which the system “knows” the relative rotational position of each prop shaft appears to be sufficient to allow future addition of a prop-phase relationship control. Vibration and noise can be minimized with careful control of the relative position of the blades on one prop with those on the other prop. This technique is common on many multiengine aircraft and is called prop phasing.

In a diesel electric system, the engine can be mounted virtually anywhere in the hull and in whatever orientation is required to achieve optimum use of space. With no need to provide a mechanical power-transfer connection to the hull, the engine mounts can be chosen for optimum vibration isolation. If desired, the engine can be totally enclosed in a sound shield, providing superior sound attenuation without the need to insulate an entire compartment. The incorporation of thrust bearings on the prop shafts ensures precise alignment with the “P” bracket and the prop-drive gearbox, reducing wear on the cutlass bearing and shaft noise. The small size of the prop-drive motor and gearbox also makes it possible to locate the props at the most advantageous position on the hull-a great advantage.

A typical Siemens single-engine twin-prop diesel electric propulsion system is comprised of a permanent magnet three-phase alternator powered by the diesel engine through a speed-increasing gearbox, two short-circuit-proof solid state power inverter modules, two 3-phase permanent magnet prop-drive motors, associated prop-drive gearboxes, a control computer and a conventional-appearing helm control station. System components are surprisingly compact and lightweight. The 145 kW (194 hp) alternator suitable to power a 48-foot trawler yacht is 10 inches square, 22 inches long and weighs 264 pounds. Each of the 114 hp drive motors is similar in size and weight. The 40 x 23 x 7 inch inverter modules are typically bulkhead mounted. The spiral bevel gearboxes used to connect the alternator to the driving engine and the drive motors to the propellers are 98 percent efficient and have a medium duty life expectancy of 25,000 hours. Gearbox power capacities range from 150 to 600 hp, meaning that they can be coupled to multiple alternators or motors to meet the power requirements of larger vessels. All of the system’s power-handling components, alternators, motors, gearboxes and power inverters are cooled with a circulating flow of water/glycol. The system is also continuously monitored, by using temperature sensors built into the alternators, motors, gearboxes and inverters.

Operating efficiency is an important part of the evaluation of any power delivery system. Although the alternators, inverters, motors and gearboxes used in the Siemens system operate efficiently, the total energy loss through the system will typically exceed the losses imposed by a conventional marine gear-coupled drive. However, the efficiency loss is to a large degree offset by the ability of the electronic control to precisely match the engine’s power curve to the vessel’s propellers. In a conventional direct mechanical prop-drive system, the fixed pitch propeller can be matched to the engine and the hull at only one point, maximum engine rpm. At all other engine speeds the engine turns faster than is necessary to produce the required power. The diesel electric drive matches the prop load to the engine, producing a result similar to that achieved with use of a controllable pitch prop. Using one large engine to power two propellers can provide an efficiency advantage compared with use of two engines providing the same total power. Depending on the positioning of the engine, power loss due to exhaust backpressure may be less than what can be achieved in a conventional installation. The option of drawing the vessel’s AC house power from the propulsion system when under way, eliminating the need to run the vessel’s genset, can improve fuel efficiency. Overall, the fuel economy of the diesel electric drive will be close to or as good as what can be achieved using a direct-drive system.

In many installations the cost of a single-engine twin-prop diesel electric power system will be no more than a conventional twin-engine direct-mechanical drive installation. Properly integrated into the design of the vessel, the diesel electric drive’s many attributes will likely make it the preferred propulsion system for a growing number of yachtsmen.

Contact: www.sea.siemens.com/marine/ .

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Volvo Penta D4 Hybrid first look: Is this the future of boat propulsion?

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Hugo Andreae gets an exclusive insight into Volvo Penta’s plans for a range of new diesel electric hybrid engines, starting with the Volvo Penta D4 Hybrid…

Volvo Penta has revealed a fascinating insight into its greener future with the launch of its first diesel electric hybrid leisure boat engine.

Although still a prototype, it is based on a standard 320hp D4 engine and DPI sterndrive with an electric motor/generator added to the driveline.

Speaking exclusively to MBY , sales project manager, Jonas Karnerfors, has confirmed that this will form the basis of a range of production Volvo Penta D4 and D6 hybrid engines.

To assess how well it works in the field, two of the prototype engines have been fitted to a 50ft aluminium fast cruiser.

Built by Marell Boats Sweden and operated by Hurtigruten Svalbard, a Norwegian-based adventure travel company, it will take visitors into the remote and environmentally sensitive waters of the Svalbard archipelago approximately halfway between Norway and the North Pole.

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The sub-zero temperatures and long running hours (it is expected to clock up 1,000 hours this year) will provide a rigorous test of the engines’ reliability, while their ability to run almost silently in electric boat mode should minimise disruption to wildlife and improve the visitor experience.

Hybrid modes

Volvo is not yet ready to share full technical details of the new hybrid engine, such as the power rating of the electric motor or size of the lithium ion battery pack, but has confirmed to MBY that the parallel hybrid system will offer three different driving modes: electric, hybrid and power.

In electric mode, it will only be capable of speeds up to around 10 knots but should be able to cruise at 5-6 knots for up to five hours, giving a range of around 30nm on battery power alone.

In hybrid mode the system itself will select whether to use the electric motor, the diesel engine or both depending on a number of different factors such as speed and battery state. In power mode both the diesel engine and electric motor will run concurrently to boost acceleration and speed.

The electric motor adds less than 500mm to the length of a D4. The battery is mounted remotely.

In fact, the electric motor actually replaces the mechanical supercharger normally fitted to the D4 and D6 engines by providing a similar torque boost to bridge the throttle lag at low RPM before the turbochargers kick in.

In the case of the Hurtigruten boat, the two 320hp hybrid engines are expected to deliver a top speed of 32 knots and a constant cruising speed of 25 knots.

Although the electric motor will be fully integrated into the driveline, adding less than 500mm to the length of the engine, the battery itself can be fitted remotely to ease packaging constraints in the engine bay.

The Marell M15 is an ideal test bed for the new technology combining lots of high and low speed running in sub-zero conditions

This can either be charged in the marina to minimise fuel burn or while the diesel engine is running. In the latter case, the system’s control unit is programmed to take advantage of the unused potential between the power that it is currently being used to propel the boat and its actual peak efficiency to recharge the batteries as efficiently as possible.

Both the driving and charging modes can be selected manually by the operator or left in fully automatic mode for the engine management system to decide.

Crucially, Volvo is determined to offer the hybrid drivetrain as an off-the-shelf package that includes the battery and propulsion unit rather than letting boat manufacturers or customers choose their battery supplier.

It hasn’t yet committed to a launch date for the production units but did indicate to MBY that it was likely to be within the next five years.

One of the big determining factors will be the size, availability and price of the battery packs. At the moment this is by far the most expensive component of the hybrid package, more than tripling the cost of a conventional Volvo Penta D4 diesel engine.

The hope is that battery density and price will come down substantially in the next few years as the drive towards electric vehicles brings reduced production costs.

Pay as you go

In the meantime Volvo is experimenting with a new form of pay-by-the-hour billing that will see Hurtigruten’s owners charged according to kW hours of engine use rather than the much higher upfront capital expenditure of buying the engines outright.

Volvo says this is an experiment in what it calls “e-mobility as a service”, and is said to be attracting a lot of interest from commercial operators.

However, it’s harder to see how the numbers would add up for leisure boat owners, who typically only run their engines for around 50-60 hours a year.

The ability to cruise in silence for up to 5 hours at a time will be ideal for wildlife watching in Svalbard. Photo: Daniel John Benton

The pilot programme is being run in partnership with Marell Boats and the Hurtigruten Group, giving Volvo a vital insight into how the new engines will integrate into the boat manufacturing process as well as how they perform in a real world environment.

Volvo is confident that the hybrid engines’ longer footprint should fit into the majority of existing boats’ engine bays but finding a suitable space for the batteries that doesn’t upset the weight distribution may prove trickier on some craft.

Volvo Penta D4 Hybrid test results

Jonas is confident that by the end of the season, the Hurtigruten test will have provided all the information needed to finalise the technical specification of the production engines.

That will just leave the question of when to make them available to the wider public and at what price they will be offered.

Either way Volvo is adamant that it is committed to launching a full range of hybrid engine solutions, not just for the D4 and D6 engines but right across its marine portfolio, including its larger IPS offerings.

“Our aim is to be the world leader in sustainable power solutions,” Jonas explains. “To do this we want to partner with companies that have the vision and courage to join us.”

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The Promises and Pitfalls of an All-Electric Yacht

• By Tim Murphy
• Updated: November 8, 2021

This past October, I saw one of the most interesting exhibits in more than 500 new cruising sailboats I’ve reviewed over two decades. It was the Arcona 435Z, built in Sweden and introduced by Graham Balch of Green Yachts in San Francisco. Balch describes his business as “a new brokerage dedicated to the electric revolution on the water,” and it was the “Z” in the boat’s name, which stands for “zero emissions,” that made this boat so interesting. This was the first electric propulsion system—not hybrid but all-electric —I’d ever seen on a cruising sailboat.

Electric propulsion isn’t new. Since 1879, electric motors have propelled boats; a fleet of some four-dozen electric launches transported visitors around the 1893 Colombian Exposition in Chicago. But cruising sailboats are not launches, and the open sea is not a protected canal. When we’re using cruising boats as they’re meant to be used, they seldom end their day plugged into a shore-power outlet. Cruising boats comprise many devices —stove, refrigerator, freezer, windlass, winches, autopilot, radar, lights—whose power typically comes from a tank of fossil fuel. And today’s cruising sailors are accustomed to using diesel auxiliary power to motor through lulls or punch into headwinds and seas.

Starting about 15 years ago, we saw a wave of diesel-electric and hybrid propulsion systems on production and custom cruising boats ( see “Perpetuated Motion,” CW , March 2005 ). Both of those systems ultimately start with an onboard internal-combustion engine. A diesel-electric propulsion system relies on a running genset to directly power the electric motor that turns the propeller. A hybrid system relies on batteries to power the electric motor, plus an internal-combustion genset to recharge the batteries. One of the promises of a hybrid system is the ability to regenerate electrical power. Regeneration means using boatspeed under sail to turn the propeller, whose spinning shaft sends electrons from the electric motor back through an electronic controller to recharge the batteries. In such a system, the boat’s propeller is both an electrical load (when running under power) and a charging source (when sailing in regeneration mode).

The Arcona 435Z was different from both of these systems: It incorporates no onboard fossil-fuel engine at all. Instead, it has a bank of lithium batteries, several solar panels, and a proprietary propulsion leg that looks like a saildrive. “This boat,” Balch said, “has the very first production unit in the world of Oceanvolt’s newest electric propulsion system, called the ServoProp.”

For our sea trial, Balch was joined by Derek Rupe, CEO of Oceanvolt USA. “If you can sail the boat and you have some solar, you can go anywhere in the world, and you can make all your power underway while you go,” Rupe said. When we spoke in October 2020, he touted three high-profile sailors who were using the Oceanvolt electric propulsion system: Alex Thomson, for his Hugo Boss Open 60 Vendée Globe program; Jimmy Cornell, for his Elcano 500 expedition; and Riley Whitelum and Elayna Carausu, who had been teasing their new boat for months on their popular Sailing La Vagabonde YouTube channel.

The efficiency of Oceanvolt’s ServoProp and the regeneration from it is the promised game-changer in each of these boats. The ServoProp is a leg with a ­feathering propeller that can be set for optimal pitch in three modes: forward, reverse and regeneration.

“You don’t need fuel,” Rupe said. “You don’t need to dock; you can go anywhere you want to go and always have the power for living and propulsion.”

That’s the promise. But are there also pitfalls?

Innovation and Risk

Marine electric propulsion is an emerging technology. Compared with the mature and settled technology of diesel engines and lead-acid batteries, electric-propulsion systems—with their electronic controllers and lithium batteries—are in a stage of development best described as adolescent. Every sailor has his or her own tolerance for technical innovation. For the promise of fewer ­seconds per mile, grand-prix-racing sailors willingly trade a high risk of expensive damage to the sails, rig or the boat’s structure itself; cruising sailors, by contrast, tend to favor yearslong reliability in their equipment as they seek miles per day.

Folks who identify as early adopters take special joy in the first-wave discoveries of a new technology; if they’re clear-eyed about supporting an ongoing experiment, they see themselves as partners with the developers, accepting failures as opportunities for learning. Sailors motivated primarily by changing the trajectory of climate change might be especially willing to modify their behavior to limit their own output of greenhouse gases. Investing in any emerging technology asks you to start with a clear assessment of your own risk tolerance. We’ll return to this theme with one or two real-life examples.

The American Boat and Yacht Council, founded in 1954, sets recommended standards for systems installed on recreational boats. For decades, ABYC has published standards related to installations of diesel and gasoline engines, as well as electrical systems based around lead-acid batteries. By contrast, it was only three years ago that ABYC came out with its first electric-propulsion standard (revised July 2021). And only last year it published its first technical-information report on lithium batteries (a technical-information report is an early step toward a future standard). The takeaway is that if you need help servicing your diesel engine or electrical system built around lead-acid batteries, you can pull into any reasonable-size port and find competent technicians to help you. With electric propulsion and lithium batteries, that pool of skilled talent is significantly scarcer.

To say that a technology is mature simply means that we’ve learned to live with it, warts and all, but that it holds few remaining surprises. Certainly, diesel-propulsion and lead-acid-battery technologies each leave plenty of room for improvement. When a charge of fuel ignites in the combustion ­chamber of a diesel engine, some three-quarters of the energy is lost in heat and the mechanical inefficiencies of converting reciprocating motion to rotation. Lead-acid batteries become damaged if we routinely discharge more than half of their capacity. During charging, they’re slow to take the electrons we could deliver.

Lithium batteries are comparatively full of promise. Their power density is far greater than that of lead-acid batteries, meaning they’re much lighter for a given capacity. They’re capable of being deeply discharged, which means you can use far more of the bank’s capacity, not merely the first half. And they accept a charge much more quickly; compare that to several hours a day running an engine to keep the beers iced down.

But the pitfalls? Let’s start with ABYC TE-13, Lithium Ion Batteries. Some of its language is bracing. “Lithium ion batteries are unlike lead-acid batteries in two important respects,” the report says. “1) The electrolyte within most lithium ion batteries is flammable. 2) Under certain fault conditions, lithium ion batteries can enter a condition known as thermal runaway, which results in rapid internal heating. Once initiated, it is a self-perpetuating and exothermic reaction that can be difficult to halt.”

Thermal runaway? Difficult to halt? Self-perpetuating?

“Typically, the best approach is to remove heat as fast as possible, which is most effectively done by flooding the battery with water,” TE-13 continues, “although this may have serious consequences for the boat’s electrical systems, machinery, buoyancy, etc.”

If you were following the news in January 2013, you might remember the ­story of Japan Airlines Flight 008. Shortly after landing at Boston’s Logan Airport, a mechanic opened the aft ­electronic equipment bay of the Boeing 787-8 to find smoke and flames billowing from the auxiliary-power unit. The fire extinguisher he used didn’t put out the flames. Eventually Boston firefighters put out the fire with Halotron, but when removing the still-hissing batteries from the plane, one of the ­firefighters was burned through his ­professional protective gear.

Samsung Galaxy cellphones, MacBook Pro laptops, powered skateboards—in the past decade, these and other devices have been recalled after their lithium batteries burned up. In that period, several high-end custom boats were declared a total loss following failures from lithium batteries. In March 2021, a 78-foot Norwegian hybrid-powered tour boat, built in 2019 with a 790 kW capacity battery bank, experienced thermal runaway that kept firefighters on watch for several days after the crew safely abandoned the ship.

Yes, experts are learning a lot about how to mitigate the risks around lithium batteries. But we’re still on the learning curve.

ABYC’s TE-13 “System Design” section starts, “All lithium-ion battery ­systems should have a battery ­management system (BMS) installed to prevent damage to the battery and provide for battery shutoff if potentially dangerous conditions exist.” It defines a bank’s “safe operating envelope” according to such parameters as high- and low-voltage limits, charging and discharging temperature limits, and charging and ­discharging current limits.

Graham Balch takes these safety recommendations a step further: “To our knowledge, the BMS has to monitor at the cell level. With most batteries, the BMS monitors at the module level.” The difference? “Let’s say you have 24 cells inside the battery module, and three of them stop working. Well, the other 21 have to work harder to compensate for those three. And that’s where thermal events occur.”

Balch followed the story of the Norwegian tour boat this past spring. He believes that the battery installation in that case didn’t meet waterproofing standards: “The hypothesis is that due to water intrusion, there was reverse polarity in one or more of the cells, which is worse than cells simply not working. It means that they’re actively working against the other cells. But if the BMS is monitoring only at the module level, you wouldn’t know it.”

On the Green Yachts website, Graham lists five battery manufacturers whose BMS regimes monitor at the cell level. “If I were sailing on an electric boat, whether it be commercial or recreational, I would feel comfortable with having batteries from these five companies and no other,” he said.

The broader takeaway for today’s sailors is that lithium batteries bring their own sets of problems and solutions, which are different from those of conventional propulsion and power-supply technologies. A reasonably skilled sailor could be expected to change fuel filters or bleed a diesel engine if it shuts down in rough conditions. With lithium-ion batteries aboard, an operator needs to understand the causes and remedies of thermal runaway, and be ready to respond if the BMS shuts down the boat’s power.

Real-World Electric Cruising Boats

When we met Oceanvolt’s Derek Rupe a year ago, he and his wife had taken their all-electric boat to the Bahamas and back the previous season. Before that, he’d been installing electric-propulsion packages for six years on new Alerion 41s and other refit projects. “My real passion is on the technical side of things—installations, really getting that right. That’s half the picture. The technology is there, but it needs to be installed correctly.”

When talking to Rupe, I immediately encountered my first learning curve. I posed questions about the Oceanvolt system in amps and amp-hours; he responded in watts and kilowatt-hours. This was yet another example of the different mindset sailors of electric boats need to hold. Why? Because most cruising boats have just one or two electrical systems: DC and AC. The AC system might operate at 110 or 220 volts; the DC side might operate at 12 or 24 volts. On your own boat, that voltage is a given. From there we tend to think in terms of amps needed to power a load, and amp-hours of capacity in our battery banks. Going back to basics, the power formula tells us that power (watts) equals electrical potential (volts) times current (amps). If your boat’s electrical system is 12 volts and you know that your windlass is rated at 400 watts, it follows that the windlass is rated to draw 33 amps.

But an all-electric boat might comprise several systems at different voltages. A single battery bank might supply cabin lights at 12 volts DC; winches and windlasses at 24 volts DC; the propulsion motor at 48 volts DC; and an induction stove, microwave and television at 110 volts AC. A DC-to-DC power converter steps the voltage up or down, and an inverter changes DC to AC. Instead of translating through all those systems, the Oceanvolt monitor (and Derek Rupe) simply reports in watts coming in or going out of the bank.

“We keep all our thoughts in watts,” Rupe said. “Watts count in the AC induction. They count in the DC-to-DC converter. They count the solar in. They count the hydrogeneration in. And the ­power-management systems tracks it that way for shore-power in.

“On a boat like this, maybe I have 500 watts coming in the solar panels,” he continued. “So then I can think: ‘Well, my fridge is using 90 watts. My boat has an electric stove. When I cook a big meal, I can see that for every hour we cook, we lose about 10 to 12 minutes of our cruising range.’”

During his Bahamas cruising season, Rupe observed that on days that they were sailing, the combination of solar panels and hydroregeneration supplied all the power he and his wife needed. “When we weren’t sailing,” he said, “we found that we were losing 8 percent each day, in the difference from what the sun gave us to what we were using for the fridge, lights, charging our laptops, and all that stuff.”

Rupe’s solution? “Twice in Eleuthera and once outside Major’s, we went out and sailed laps for a couple of hours because the batteries were below 30 percent of capacity. It was good sailing, and the wind was coming over the shore, so we didn’t have any sea state. We did a couple of hot laps on nice beam reaches, and generated about 700 watts an hour.”

Of the three sailors Rupe touted in October 2020—Alex Thomson, Jimmy Cornell and the Sailing La Vagabonde couple—only Cornell can report back on his all-electric experiences with Oceanvolt. Alex Thomson ended his circumnavigation abruptly last November, just 20 days after the Vendée Globe start, when Hugo Boss collided with an object in the South Atlantic. And at press time in early fall 2021, Riley and Elayna had just recently announced the build of their new Rapido trimaran; keep an eye on their YouTube channel for more about their experiences with the Oceanvolt propulsion system.

As for Cornell—circumnavigator, World Cruising Routes author, creator of the transoceanic rally, and veteran of some 200,000 ocean miles—he suspended his planned Elcano 500 round-the-world expedition solely because of the Oceanvolt system in his new Outremer catamaran. His Aventura Zero Logs on the Cornell Sailing website, particularly the Electric Shock article posted on December 2, 2020, are essential reading for any sailor interested in sailing an electric boat. “Sailing around the world on an electric boat with zero emissions along the route of the first circumnavigation was such a tempting opportunity to do something meaningful and in tune with our concern for protecting the environment that my family agreed I should do it,” Cornell wrote. “What this passage has shown was that in spite of all our efforts to save energy, we were unable to regenerate sufficient electricity to cover consumption and top up the batteries.”

Cornell’s experience in that article is raw, and his tone in that moment bitterly disappointed. We recommend it as essential reading—not as a final rejection of the electric-boat concept or of Oceanvolt’s system, or even as an endorsement of Cornell’s own decision that the system didn’t work. I suspect that I may have arrived at the same conclusion. Yet given the same boat in the same conditions, one imagines that a new breed of sailor—a Graham Balch or a Derek Rupe—may have responded differently to the constraints imposed by an all-electric boat, as nearly every cruising sailor today habitually responds to the inconvenient constraints of diesel engines and lead-acid batteries.

“If you bring electric winches, electric heads and an induction stove, and then sail into a high-pressure system, you’ll set yourself up for failure,” Balch said. “You have to balance your power inputs and your power outputs.

“Sailing an electric boat is a return to the tradition of sailing that the crutch of a diesel engine has gotten us away from,” he added. “Magellan’s fleet got all the way around the world, and they didn’t have a diesel engine.”

Tim Murphy is a Cruising World editor-at-large and ­longtime Boat of the Year judge.

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How hybrid sailing yachts finally became a feasible option

• May 17, 2019

They’ve been a long time coming, but marine hybrid propulsion systems are finally a working reality, as Sam Fortescue reports

The Bootswerft Heinrich-built 13m Yamila uses an Oceanvolt electric motor rather than a diesel engine. Photo: Peter Minder

Every sailor is familiar with the wet cough of the diesel engine, and the acrid smell of its exhaust. For some it’s the sign that an adventure is starting, for others it is the reassurance that all is well on board the boat. The traditional engine is perhaps your boat’s most important safety feature, but its days may be numbered.

The electric sailing revolution is coming – and though adoption in the marine sector is proving much slower than in the automotive world ashore, progress is being made.

The market is still relatively small. Clear market leader Torqeedo had sales of €25m last year, most of which was in ferries and compact outboards. It also offers a range of saildrive and pod drive motors for yachts displacing from 2 to 50 tonnes, or roughly 20-60ft LOA.

But sailors have been slow on the uptake, and for one good reason: if you’re planning to cross an ocean or take on tough conditions offshore, you rely on your engine to help you outrun danger or motor through the doldrums – sometimes for days at a time.

Oceanvolt AXC series is a modular shaft drive system (10kW to 40kW) that will fit in place of a tradition diesel engine

Even with the current crop of advanced lithium-ion boat batteries , the range of an electric system is measured in tens of miles, not hundreds. So a 35ft monohull with 10kWh of lithium battery (four units weighing 96kg in total) would have a range of just 24 nautical miles at 3.8 knots, or less than 16 nautical miles at full throttle.

Taking into account the incredible wastage of combustion engines, which dissipate more energy as heat and noise than they provide in propulsion, diesel is still ten times more energy dense than batteries.

Full-carbon luxury daysailer Yamila uses an Oceanvolt SD8 8kW electric saildrive system. Photo: Tobias Stoerkle

“When you look at bluewater cruisers, of course you will have a diesel,” says Torqeedo’s founder and CEO, Dr Christoph Ballin. “And it’s right that not many coastal sailors opt for pure electric.”

But that doesn’t mean that electric has no interest for cruising sailors – far from it. The more common route for ‘normal’ sailors will be to combine diesel and electric in a hybrid sailing system.

Under this model, the engine is replaced by an electric motor, hooked up to a bank of lithium batteries. This can be charged via hydrogeneration – when the speed under sail turns the propeller and puts charge back into the batteries – and solar or wind. But when extended periods under power are required a standalone DC generator, which can be installed anywhere on board, supplies the electricity.

This is the set-up recommended by Finland’s Oceanvolt, which has focused on the cruising sailing market with a range of shaft and sail drive motors from 3.7kW to 15kW (roughly 10hp to 45hp in diesel engine terms).

“In the case of the round-the-world cruiser, we recommend a hybrid system with a backup genset to support continuous drive when/if needed,” says Oceanvolt CEO Markus Mustelin. “A regenerating prop, which spins while sailing and recharges the batteries (sacrificing 0.2-0.4 of a knot, depending on the boat and conditions) makes it possible to be almost independent of the genset and use it only for backup.”

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This system has the advantage that the generator is only needed on longer passages, so the boat still manoeuvres silently in and out of ports and anchorages.

And a well-designed, correctly sized generator is much more efficient at turning diesel into electricity than an engine not originally designed for the job. Some sailors opt for an in-line hybrid system, like those offered by Hybrid-Marine, which bolts onto the existing diesel.

These are easier to retrofit, with many of the same characteristics as the full hybrid system, but there’s the disadvantage of still having an engine boxed away somewhere near the middle of the boat.

Electro magnetism

Until now, most business has been done through retrofitting existing yachts. But an increasing number of yacht builders are looking to include electric propulsion as original equipment. The world’s third largest boatbuilder, Hanse Yachts , is perhaps the most advanced – offering its entry-level Hanse 315 with an electric rudder-drive option.

The system takes up less space than the standard diesel, is much quieter and vibration- and emissions-free. But Hanse admits take up has been disappointing.

The technology has found more interest among lake sailors. Innovative young German brand Bente has been fitting Torqeedo motors to its successful 24ft model, originally designed for Germany’s ‘Green Lakes’.

Closer to home, dinghy specialist RS Sailing has decided to fit a retractable electric drive to its new RS21 keelboat. Already christened the ‘invisible gennaker’, the system is based on Torqeedo’s Travel 1003 outboard motor.

Bigger race boats have also been attracted by the lure of low-weight propulsion. Just look at Malizia , an IMOCA 60 being prepared for the 2020 Vendée Globe with a lightweight Torqeedo system.

“Emissions-free round the world under race conditions, while simultaneously producing your own energy, is a thoroughly inspirational concept,” said Malizia skipper Boris Herrmann.

Electric has also been successful at the luxury end of the market, where lithium-ion batteries account for a smaller share of the boat’s overall cost. A 50ft Privilege 5 catamaran and a carbon fibre Gunboat 60 have both been retrofitted with Torqeedo kit, while Oceanvolt appears on a Swan 57 and an all-carbon Agile 42.

Overview of the Torqeedo Deep Blue propulsion system installed in the Gunboat Moonwave

The Gunboat Moonwave has two 25kW Deep Blue saildrives both capable of regenerating under sail. There is still a generator on board to extend battery range offshore, but “they no longer use the generator – it’s just for emergency,” says Torqeedo’s Ballin.

Spirit Yachts is also designing electric propulsion into its Spirit 111  flagship, due for launch this summer. With four big 40kW lithium batteries aboard and a 100kW motor, the yacht will be able to operate silently for hours, although it also has 100kW of diesel generator capacity.

“The real focus is not the propulsion,” explains Spirit director Nigel Stuart, “but that everything works in harmony, from galley equipment and hot water to heating, air conditioning, hydraulics etc.” The British yard is also building a 65-footer using Oceanvolt hybrid technology and a new 44-footer that is pure electric.

With racing on one hand and high-end cruisers on the other, there is something of a gap in the middle. By Torqeedo’s own admission, the cruising sailor hasn’t been a big focus of the electric revolution, but all that is about to change. “We started a bit late with sailing,” Ballin admits, “but in the next five to eight years it will be addressed big time.”

Fully integrated electric drive system will power the new 111ft Spirit Yachts flagship

What does that really mean? Well, in the first instance, it means system integration. If that doesn’t sound revolutionary, then imagine a set-up on board where solar panels, hydrogenerators, batteries, generators and motors all worked seamlessly together to keep the yacht supplied with ample power around the clock. “That’s what people are willing to pay for: plenty of energy with heating or air-con through the night,” says Ballin.

The future of hybrid sailing

In the near future, Torqeedo is planning a new range-extending DC generator specifically for hybrid sailing boats. Its existing unit is built by WhisperPower and provides 25kW, which is too much power for boats using the pod drive system.

The genset will be designed to operate at optimum revolutions, while clever DC to DC conversion decouples the battery voltage from the charging voltage, for much greater efficiency.

With boats, just as with cars, the breakthrough that will make all the difference is around battery capacity. Until range under electric power can match that of diesel, there will be many sceptics. And that isn’t likely to happen for a decade or more, according to Ballin.

“Theoretically, they’ve tested batteries in labs that are ten times more efficient than lithium,” he explains. “And if that comes through, then gasoline is done. But we are trying to combine long-term vision with short-term mindset.”

In the meantime, the prevalent technology is based on lithium-manganese-cobalt, and a process of steady development is making this 5-8% better each year. For example, BMW has just announced its next generation i3 battery, used by Torqeedo’s Deep Blue system, will be able to hold 40kWh of power – an increase of 33% for the same size, weight and nearly the same cost.

Torqeedo Cruise 2.0 FP Pod Drive is suitable for small yachts up to 4 tonnes – a folding prop can also be fitted

The other area of development is around the propeller. Most cruising systems use a folding or feathering prop designed for diesel engines. But Torqeedo’s own research shows that the consistently high torque of an electric motor is best utilised by props with variable pitch.

And yet it is Oceanvolt that has addressed this issue specifically for electric motors with its Servo Prop system, which it claims to be 30% more efficient ahead, 100% better astern and 300% more efficient in regeneration mode.

Oceanvolt says that this prop can pump around 500W into the batteries at just 5 knots – the average pace of a 30ft monohull. At 6 knots that rises to around 800W, and at a very manageable 7 knots for a larger ocean cruiser you get 1.2kW.

“A new technology can rarely compete in price with an established one in its initial growth phase,” says Mustelin. “However, we have passed this and today electric systems are offered at a quite competitive price. When you add to that the fact the electric system is almost service free, the total cost of ownership is turning in favour of electric.”

So, you may not hear them approach, but expect to see more and more electric-powered boats on the water as the revolution continues.

A question of torque

A key part of the viability of electric propulsion rests on the notion that a smaller motor can achieve the same work as a bigger diesel. There are two elements to this. First, a diesel engine is not an efficient converter of chemical energy into thrust, creating a lot of heat and noise in the process. Second, the torque characteristics of electric are much better than diesel.

Mustelin says that Oceanvolt’s 10kW motor “easily outperforms” a 30hp diesel. “Typically, maximum boat speed will be somewhat lower (0.5kt-1.0kt) than with a comparable diesel engine, but at the same time the boat will maintain the speed better in heavy seas and headwind due to higher torque. Manoeuvrability is much better in confined marina spaces.”

That’s because combustion engines only reach peak power (and maximum torque) over a small range of speeds. Torque is a measure of turning power – at the propeller in the case of a boat.

A diesel engine develops optimum torque between 1,800-2,000rpm, while electric motors deliver it from 0 to around 2,000rpm. This allows electric motors to use higher efficiency propellers that are slimmer and more steeply pitched.

Engine-driven: The ‘alternator on steroids’

It has taken years of development and over $10m of funding, but renowned boat systems expert Nigel Calder has helped design an alternator so powerful that it eliminates the need for a generator on board.

Mounted on the engine, on the second alternator position, the Integrel can produce five to ten times more power. Sitting behind the system is at least 10kWh of lead acid batteries (lithium is also an option), and Victron chargers and inverters.

“If you crank the engine it’ll charge the batteries; if you’re running with the engine in neutral, it’ll know it’s in standalone generator mode and switch to that algorithm,” explains Calder. “It will likely be cheaper than a generator installation, and eliminates the issue of the through-hulls, the cooling circuits, the long running hours, the maintenance.”

The system allows you to run all sorts of creature comforts on board that would normally require a generator: from hot water on-demand to coffee makers and freezers. “We honestly believe that this system is going to supplant generators on almost all boats that currently have, or would like to have, a generator,” adds Calder.

With the engine in gear and at low revs, tests show how the Integrel can produce some 2kW of power without increasing fuel consumption or reducing speed – simply utilising the engine’s wasted capacity. This means it will work with the yacht’s existing engine – no need to overspec – and it has already been successfully installed on a new Southerly 480, a Malo 46 and a similar-sized Hallberg-Rassy.

Case study: Dufour 382 Alcyone

Built by Dufour in 2016, Alcyone was immediately retrofitted professionally with Oceanvolt’s SD15 saildrive motor, supplied by a 14kWh lithium battery bank. Owners Michael Melling and Diana Kolpak also specced an 8kWh DC generator for range extension. The fit out cost €30,600 for the motor and battery system, plus an additional €13,744 for the generator, and installation costs were around €8,000.

They charter the boat out near Vancouver, for exploring Desolation Sound and the surrounding area where silent, clean propulsion is a selling point. “Nothing spoils the joy of sailing – or a secluded anchorage – more than the noise and smell of diesel engines,” they explained. “Installing an Oceanvolt system in our new boat has freed us from that. It’s the way of the future.”

Charter manager Merion Martin said the conversion has also been popular with charter customers, adding: “The main advantage of the system is that it consistently uses around 40% less fuel than a standard diesel engine over the course of a week’s charter. But understanding the power management system takes a bit of getting used to, and the many components involved in the system can make troubleshooting a challenge.”

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Diesel Electric Propulsion: Is This A Safer, More Efficient Solution For Your Vessel?

• June 18, 2017
• Quite Interesting

Although the idea of powering your vessel with the indirect, two-step diesel electric energy transfer system may appear to be unnecessarily complex, its many advantages can make it a compellingly attractive alternative to a conventional direct mechanical prop-shaft drive. When under way all of the electrical power required by the vessel can be supplied from the diesel electric propulsion system, eliminating the need to run a genset.

A diesel electric power system can drive multiple propellers from a single engine or use multiple engines to power one or more propeller. In a twin-engine/twin-prop system, one engine can power both props when operating within the speed limits imposed in many areas. Electrical power from the vessel’s genset can be used to propel the boat, providing a built-in backup-especially valuable for vessels with single-engine installations.

Conversely, the propulsion system can serve as a backup for the gensets. The use of electric propulsion in certain vessel types is well-known. In marine applications, nearly all the energy is produced by diesel engines. Using an electric propulsion system, where the energy transmission is electrical and the propulsion and thruster are variable speed electrically driven, fuel consumption can be reduced significantly for many vessel types with environmental benefits.

Diesel Electric Systems have been in use to propel vessels for more than 100 years. Branobel launched the first diesel-electric ship in 1903, and since that day, diesel electric propulsion systems have evolved and today they can be found in all boat sizes and applications. But how do you know when to utilize diesel electric technology for your vessel? The investment in Diesel Electric vessels have doubled in the past 4 years, while the construction of purely mechanically propelled vessels have slowed down. But what are the reasons for this growth? Some of the benefits of the Diesel Electric systems are:

Effective design: The ability to locate your generators in any part of the vessel independent of where the power will be used;

Smaller Engine Rooms: Possibility to replace a big slow speed engine with multiple smaller generators;

Reduced Noise and Vibration: No need for long drivelines;

Flexibility: Capability to share the power of one unit with multiple devices (main propeller, bow thrusters, hotel load, pumps, etc);

Redundancy: Generators can be reassigned to cover any machine downtime;

Efficiency: Depending on the application the system can provide better fuel efficiency (mainly if there are requirements for long periods of low speed/load)

Fuel consumption savings calculation: The optimum operation point of a diesel engine will typically be around a load of 85 percent of the Max continuous rating (MCR). Moreover, the efficiency level drops quickly as the load becomes lower than 50 percent of MCR. With the help of the electric system, the mechanical propulsion prime mover is replaced by diesel-electric prime movers that will automatically start and stop as load demand varies. In comparison to a conventional vessel with mechanical propulsion, this enhances the efficiency of the energy usage and reduces the fuel consumption by keeping the average loading of each running diesel engine close to its optimum load point.

However, in some vessel applications, the load variations can be large and rapid. It is impossible to make the generators switch on and off every five seconds as would be the case with DP vessels. By using super-capacitors to supply the load variations, and hence let the diesel engines provide the average load, the peak power of the power plant will be reduced, allowing the average loading of the engines to increase to a more optimal point with lower specific fuel oil consumption. The savings in fuel consumption will depend on many parameters such as actual variations in the load, the average load and the number of prime movers.

In many installations the cost of a single-engine twin-prop diesel electric power system will be no more than a conventional twin-engine direct-mechanical drive installation. Properly integrated into the design of the vessel, the diesel electric drive’s many attributes will likely make it the preferred propulsion system for vessel owners and operators now and in the future.

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How superyacht diesel electric power systems work

Diesel-electric power has powered ships and submarines for nearly a century. Today, it is the subject of more discussions between owners, captains, designers and builders as a cleaner, more efficient source of on-board power and propulsion. It has been hyped as a possible ‘greener’ way forward, but is it?

What it is and how it works

When Rudolph Diesel obtained the patent for his 1.58kW Rational Heat Engine with its 10ft diameter flywheel in 1892, he never could have predicted that what came to be called the diesel engine would be as popular as it is today. Nor could he have foreseen the many uses to which the engine has been put. He might, however, recognise the diesel-electric drive train.

Such a system, quite crude by today’s standards, was installed in 1903 in the Russian tanker Vandal , while Diesel was still alive. _The Vandal’s _diesel-electric drive was a far cry from today’s systems where the driving engine and its electric generator (often called by its abbreviation, genset) might be on one part of the vessel and the motor driving the propeller might be elsewhere, even outside the hull.

There are arguments both for and against diesel-electric drives. Proponents say that emissions are lower because only the power needed is used and fuel consumption is reduced, while those against suggest that the weight of a genset and driving motor increases the overall vessel weight, which requires more horsepower to drive the yacht. Additional electrical systems also add complexity, which can cause interference with other electrical systems.

From the naval architect’s standpoint, a diesel-electric system allows the drive engine to be moved away from the end of the propeller shaft. The diesel generator can also be located away from guests to reduce noise and vibration and placed in areas of the hull not normally used for engines or people.

For example, on a 40m yacht, the area under the cockpit may not have adequate headroom for crew cabins, but a pair of diesel generators might fit easily. On vessels over 150m, a gas turbine located in the stack where hot gases can be directed up and away from the deck may be used to generate power, moving power generation completely out of the hull.

A further advantage is that a yacht equipped with several generators can carefully optimise power levels between the house and drive loads. For example, when the yacht is under way, house loads tend to be lower than when the yacht is sitting in harbour with guests aboard. This enables the electronics system to adjust generator power levels between house and powering modes so that both are operating with minimum emissions and fuel consumption.

Under way, the electronic controls monitor propulsion performance as well as house loads and adjust the generators accordingly. This eliminates running high-horsepower main engines continually and still having to adjust generator loads. The end results are lower emissions and improved fuel performance. In addition, an electric propulsion motor can easily be controlled in terms of speed and be reversed without the need for a large gearbox or transmission.

The end result is lower emissions and better fuel performance. In addition, an electric propulsion motor can easily be controlled in terms of speed

An added benefit is the fact that the drive motor can be located outside the hull in a pod drive of the type that Siemens and Schottel have developed, or an azimuthing pod drive can also be used. Using pod drives allows seawater to cool the drive motors, reduces the size of the engine compartment and cuts down on vibration and noise inside the hull. By turning the actual drives, propeller thrust is directed where it can do most good, rather than being deflected off rudders. In addition, rudders and their complexity are eliminated, improving hull drag. In addition, because thrust lines are horizontal, propeller efficiency is considerably improved.

Gensets and batteries

The number of gensets required for a successful diesel-electric installation is critical. If, for example, three large generators are used, at least one will have to operate continuously unless the vessel is on shore power. In addition, one might be under repair. Considering that an 80m yacht might require 300kW when in port, and an additional 400kW when under way, it might seem sensible to have two 400kW generators. But at anchor at night, the generator loads might go down to 100kW, thus both generators would be oversized. In this case it might be more feasible to have a smaller genset of 100kW, two of 300kW, and one of 400kW or 500kW to enable loads to be matched to power consumption to minimise emissions and fuel costs.

For silent operation, say at night, the diesel-electric system could be combined with an energy-dense lithium-ion battery bank or two. In operation, the batteries could be used to drive the pod motors or to power the house lighting for totally silent, night-time operation. The battery banks would have to be quite large to store enough power – probably around 800 to 1,000 amp-hours at 600 volts for a 60m to 70m yacht – but with today’s lithium-ion batteries, such a system is not beyond the realm of possibility.

Diesel-electric and emissions regulations

For all its appeal, diesel-electric has a few disadvantages. To start with, instead of a mechanical engineer, an owner will require an electrical engineer.

As mentioned above, the increased weight of a diesel-electric system can be a drawback. With the new emissions controls that have just come into force in various parts of the world, each genset will require its own controls, should each set be in different parts of the yacht.

Throwing a wrench into the development of diesel-electric yachts are ECAs, or Emission Control Areas. These areas are intended to cut down on NOx (nitrogen oxides) and SOx (sulphur oxides). ECAs, which recently were put in place around the coasts of North America and affect every large vessel in those waters, will necessitate the use of Selective Catalytic Reduction (SCR) to reduce NOx and low-sulphur diesel fuel to reduce SOx. Generator manufacturer Northern Lights has just introduced what it calls its Diesel Exhaust Cleaning System (DECS). The system is based on DCL International’s Marine-X system, which removes particulates as they are emitted from the engine.

Throwing a wrench into the development of diesel-electric yachts are ECAs, or Emission Control Areas. These areas are intended to cut down on NOx (nitrogen oxides) and SOx (sulphur oxides)

In a non-Northern Lights installation, to reduce NOx, a diesel exhaust fluid (DEF) tank containing urea and an atomiser pipe would need to be located near the generators. The DEF is injected into the exhaust stream to react with NOx to create nitrogen and water. To simplify this installation, the entire generator compartment may have to be located in an easily accessible place where the DEF tanks and atomiser can be used on all the generators.

Because of SCR and its associated piping, engine rooms will grow larger, but by placing the drive motors on pods outside the hull, engine room size increases can be minimised. However, this will require widespread adoption of diesel-electric drives, instead of diesels with transmissions and shafts.

Alternative fuel systems

In order to reduce emissions, commercial ship owners are experimenting with using fuels that reduce costs and do not produce much in the way of emissions. Often, where commercial shipping leads, recreational vessels follow, thus a superyacht of the future might be powered by one of these fuels. However, terminals where ships using liquefied gas can refuel may be far and few between and until the infrastructure improves considerably yachts will not follow this trend.

A hydrogen-fuelled superyacht has been proposed. It is a 64m hydrogen diesel-electric yacht from Pharos Marine in Egypt. Given the explosive nature of hydrogen and the lack of refuelling facilities, though, this is more a marketing concept than a real project.

In the far longer term, nanotechnology could lead to major advances in solar and wind power generation. Combined with advances in electric motor and battery technology, nanotechnology could change the look and style of superyachts as we know them today.

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Electric and Hybrid Propulsion for Sailboats

Practical sailor looks at the players in the developing field of electric auxiliary engines.

How soon will electric auxiliary propulsion be available to everyman? That depends on whom you ask. Opinions differ widely not just on what type of drive system might surge to the forefront, but even on whether the concept itself is viable. While a handful of companies forge ahead, notably Glacier Bay and Electric Marine Propulsion on this side of the Atlantic, some expected participants are waiting on the sidelines.

Photos courtesy of Manufacturers

One of the big issues that divides promoters and detractors alike is whether the appropriate way to go in a sailboat is with a pure diesel-electric drive train, with a hybrid electric drive with a diesel generator as back-up, or as a pure electric drive with regeneration capability. We’ll take a look at these and other options later in this article. For now, the short answer is that no single approach suits every sailor all the time.

Simply put, in the diesel-electric system, the electric motor runs only when the diesel-driven generator is running. Such arrangements have long been employed in railway locomotives, submarines, and commercial vessels of many types. In the hybrid system, a large bank of batteries provides the energy for the electric motor and the diesel generator recharges the batteries. On the face of it, the hybrid system offers a certain degree of redundancy in that, assuming the batteries are kept well charged, the boat has a measure of emergency power should the generator fail at an inopportune moment. The hybrid also is capable of recharging its batteries when sailing: Driven by the turning propeller, the motor becomes a generator.

Each of these approaches has its strengths and weaknesses, and while we’ll leave it to their developers to work out the technical issues, we would like to urge anyone contemplating installing an electric drive, or purchasing a boat that has one, to first look very closely at how they expect to use the boat. There’s more entrained in the choice than in picking a flavor at Baskin-Robbins. More on this later.

Among the electric drives currently available in one form or another, or as components, the big variable is operating voltage. Motors are available that run on 24, 36, 48, 72, and 144 volts, and, in the case of Glacier Bay’s diesel-electric system with Ossa Powerlite technology, 240-volt DC. Each supplier will discourse at length on the merits of their voltage choice, but an inconvenient fact haunts the entire field: High-voltage DC is deadly, potentially more so in some circumstances than AC.

While neither form of high-voltage is “safe,” we have a lot more experience with AC aboard recreational vessels than with high-voltage DC. An extensive body of knowledge exists on which to base AC installations so as to make them safe as well as reliable. High-voltage DC is used in a variety of marine and non-marine commercial applications, but these installations are well protected from access by untrained operators.

What voltage constitutes high voltage? That, again, depends on whom you talk to. The American Boat & Yacht Council (ABYC), which sets voluntary standards for the marine industry, defines it as 50 volts and above. Prompted by rapid adoption of high-voltage services in small commercial craft and bigger yachts, though not specifically in propulsion systems, the ABYC is in the process of drawing up guidelines for voltages higher than the 48 volts covered by existing standards.

An absence of standards might not deter individuals from installing an electric drive, but it might impede widespread adoption of the technology. If a surveyor can’t state in an insurance survey that a boat is built according to ABYC standards, that could affect its insurability.

Jim Nolan, who manages the underwriting department for BoatUS, said the company has no clear cut guidance regarding insuring boats with electric propulsion. Each boat is dealt with on a case-by-case basis. A new boat with a factory-installed system would be a good deal easier to underwrite than a one-off or do-it-yourself project, especially in the absence of a standard practice. Lagoon Catamarans’ 72-volt-DC hybrid system, for instance, has qualified for the European standard (CE) certification on the strength of following industrial standards that apply to such applications as fork-lift trucks. Anyone contemplating an electric drive would be well advised to discuss it ahead of time with an insurer and even get a surveyor involved from the outset.

Because of the safety issues surrounding the voltages involved in electric propulsion, Fischer Panda has decided to limit its DC product line to boats weighing 10 tons or less. A company representative we spoke to said that while Fischer Panda currently sells DC generators up to 48 volts in the USA for marine use, it “won’t touch” high-voltage DC because it’s lethal.

A proposed collaboration with Catalina Yachts to fit a diesel-electric system in a Catalina-Morgan 440 never came to fruition due to budget constraints, according to Fischer Panda. But in Europe, Fischer Panda teamed up with Whisperprop to equip a Bavaria 49. (Beyond the fact that one of its boats was used, Bavaria Yachts was not involved in the project.) According to Fischer Panda, after evaluating the Bavaria project, the company decided that the diesel-electric AC system is a niche product that wouldn’t interest their prime market: original equipment builders.

“Although the AC system has some advantages in the improved response of the electric motors … and the quietness of the system, the desired fuel efficiency and weight savings were not evident,” Fischer Panda reported.

Fischer Panda considers the DC system to be more suitable for its North American customers. Although it’s limited in output due to its limited battery voltage of 48 volts, it is still able to power multihulls up to 10 tons.

Currently, much of the movement toward electric drives is taking place in the catamaran world. This makes sense when you consider that a single diesel generator can, in theory, provide all the boat’s electrical needs and also take the place of two diesel-propulsion engines. Taking the lead in the field, Lagoon Catamarans introduced in 2006 the Lagoon 420. Originally offered only as a hybrid, it now is also available in two diesel versions. Corsair Marine is building the Corsair 50 catamaran around the Glacier Bay diesel-electric drive, but the boat’s launch date—formerly set for this summer—has been postponed.

Dick Vermeulen, president of Maine Cat, tried the Glacier Bay system in a prototype power cat, but it failed to meet performance expectations, so production models will have conventional diesels. A number of other cat builders have announced hybrid or diesel-electric projects, but feedback on how they perform is scan’t.

So much for the mainstream—but backwater sailors will go their own way, as they always have. As more vendors and components enter the market, the options for do-it-yourselfers or custom-boat customers become broader and more attractive. However, before going ahead with an installation, make sure it’s appropriate to how you plan to use your boat, and even then be prepared to adapt the way you sail to take best advantage of the system’s characteristics. Here’s a rundown of the various types.

Electric Drive Only

Duffy Electric Boats has for years been building electric launches and lake boats that have the simple capability of puttering around in sheltered waters for a period of time determined by battery capacity and speed maintained. A battery charger powered by shore power charges the batteries overnight. Transferring that approach to a sailboat up to about 25 feet used for daysailing and kept near an electrical outlet shouldn’t be too difficult. It won’t offer the assurance of diesel when trying to get home against current or wind, but a proven 36- or 48-volt system will keep you out of uncharted standards territory.

For a bigger boat, more power, a greater range, or a combination of these requirements, it will be necessary to install a large battery bank and almost certainly will entail going to a higher voltage to keep the amps and the cabling needed to carry them manageable. The boat’s range under power will be limited by the weight of batteries, and while lighter lithium-based technology is on the horizon, for now the standard is lead/acid. The fast charging, but expensive pure lead thin plate (PLTP) Odyssey batteries have attracted particular interest among propulsion enthusiasts.

Electric Drive with Regeneration

The next level up in complexity is a “reversible” system. When the boat is sailing, the propeller turns the motor, which then becomes a generator. The electricity it makes is used to recharge the batteries. The capability to regenerate extends the boat’s potential range, but the drag on the propeller slows the boat measurably. One hour of regen will not restore the power consumed by one hour of motoring, but if sailing time sufficiently exceeds motoring time, this arrangement offers considerable range.

A regenerating system does have the potential to overcharge the batteries once they become fully charged and the boat continues to sail fast. The solution is, ironically, to give the motor some “throttle,” which reduces the drag on the propeller and consequently the power output. This phenomenon gives rise to a new technique, that of “electro-sailing” in which sails and an electric motor complement each other. At present, the “throttle” must be adjusted by hand, but developers are working on automatic controls. Field trials of existing regen motors such as the Solomon systems suggest that a small regen motor’s ability to match the output of a much higher-rated diesel have been overstated.

Hybrid Electric Drive

A hybrid system adds to the mix an onboard generator, which is used primarily to maintain charge in the batteries, both those for the propulsion motor and for the house services. This arrangement extends the boat’s capability to lie for long periods at anchor, independent of shore power for electricity and without the need to go sailing for the sole purpose of charging the batteries. A hybrid can motor constantly, as long as there is fuel, but it cannot sustain full speed for long periods. This is because the generator is usually rated at a far lower horsepower than that required to drive the boat at full speed.

Diesel-Electric Drive

In a pure diesel-electric, the electric propulsion motor runs only when the generator is running. Storage batteries are not needed for propulsion purposes, and the generator is the source for all onboard electrical power needs. The rationale behind diesel electric lies in the relationship between a diesel engine’s rate of fuel consumption and the load it’s working under. It burns fuel more efficiently when heavily loaded than when lightly loaded. When the diesel engine is disconnected from the propeller, it can be controlled so that it is working in the upper range of its efficiency regardless of how fast the propeller is turning. Nigel Calder’s series of articles in Professional Boatbuilder magazine (www.boatbuilder.com) beginning with the June/July issue delves deeply into the efficiency discussion surrounding these engines. Systems on large vessels are built around multiple generators that switch on or off according to the power demands of the moment. Translating those efficiencies into a smaller boat scenario has proven to be challenging.

Hype vs. Experience

Maine Cat’s Vermeulen, on the company’s website, describes the sea trials he performed in the Maine Cat 45, a power catamaran. He began with a Glacier Bay diesel-electric system with two 25-kW generators, each weighing about 550 pounds.

“With both generators putting out their full power of 25 kW each … our top speed was a disappointing 8.4 knots, and the assumption that electric horsepower was somehow more powerful than conventionally produced horsepower was in serious doubt.”

He replaced the propellers with a pair with less pitch, which allowed the electric motors to reach their full rating of 1,100 rpm, but that only increased the speed to 9.1 knots.

“These are about the same speeds and fuel burns we get on our Maine Cat 41 sailing cat … powered by twin 29-horsepower 3YM30 Yanmar diesels with saildrives and two-bladed, folding propellers.” At the time he installed them, the 25-kW generators were the highest power available from Glacier Bay.

Vermeulen replaced the diesel-electric system with twin 160-horsepower Volvo diesels. At 9.1 knots, they together burned 2.2 gallons per hour, considerably less than the 3 gallons per hour that the Glacier Bay system burned at the same speed. With the twin Volvos maxed out at 3,900 rpm, the boat made 24.5 knots.

Also among the unconvinced is Chris White, well-known designer of ocean-going catamarans. “To date, I’ve not seen any system that makes sense for a cruising boat,” he says, but he might change his mind, “if someone can show me by building one that delivers an advantage in performance, weight, or cost.”

White sees the current bubble of interest in diesel-electric drives as a fad. In the end, he says, you’re getting the horsepower the diesel creates at the crankshaft, which is basically the same whether it’s delivered to the prop via a conventional reduction gearbox or via a generator and an electric motor. Besides, he says, diesel engines and diesel fuel are understood and available anywhere in the world you might take a sailboat. Complex, electronically controlled electric motors are not.

White’s reservations notwithstanding, it’s in the world of catamarans that we’re seeing most of the applications. At first sight, it does seem logical that replacing three diesel engines—two propulsion and one generator—on a fully equipped cruising cat would result in fuel savings. Still, if the generator is big enough to drive the boat at cruising speed (which in a cat is expected to be in the vicinity of 10 knots) and run the air conditioning at the same time, it will be overkill for the times it’s only needed to operate the boat’s services. For this reason, commercial and military diesel-electric systems employ multiple generators that can be switched on and off according to the power demand of the moment.

Corsair Marine hopes that by installing a diesel-electric system in its 50-foot catamaran, it will be able to descend the weight spiral. Where a conventional installation would involve two 75-horsepower saildrives plus a 6-kW genset, it’s fitting a pair of 28-horsepower electric motors, one 25-kW generator, and a 40-amp, 230-volt battery bank. It expects to save about 700 pounds in equipment weight, some of it through the use of high-voltage, low-current systems, which will in turn reduce the rig requirement, thus the structural weight, and so on toward an estimated overall weight savings in the thousands of pounds.

Corsair’s David Renouf estimates that the boat will cruise at 8 knots and be capable of short bursts at 10. He admits that, until the first boat is launched, his information is “based on extrapolation, not proven numbers.” He says that some clients will add a second 25-kW genset to assure longer periods at 10 knots. Currently, the project is running behind schedule, with a launch scheduled before the end of the year.

Cost and Other Benefits

At the present time, there appears to be no reason to install any proprietary electric drive of any description in the expectation of bettering the economics of a standard diesel drive. The motors and their electronic controllers are sophisticated and expensive. A battery bank sufficient to provide a useful motoring range is a big investment in weight, space, and money. When you add a generator and its peripherals, the cost and weight take another upward leap.

Only the simplest system will begin to pay itself off in terms of fuel not burnt, and then only if the boat sees a great deal of use. A diesel-electric system designed to closely dovetail with the way you use the boat may prove to be more efficient over time than a conventional diesel installation, but until enough systems have been installed and used and data from that use compiled and compared, we can’t know that.

So why even consider going electric? Cleanliness and silence of operation are two qualities that make electric propulsion an attractive proposition for a sailboat, but in order to enjoy them, we have to accept the limitations they impose.

A hybrid or a diesel-electric system enables us to have a single fossil-fuel power source for both propulsion and onboard appliances, but whatever fuel we might save as a consequence of motoring more efficiently for a couple of hours will be inconsequential if we run the generator all night to power the air conditioning.

Conclusions

As we go to press, pickings are slim for sailors looking for an electric solution to the diesel problem. Suppliers of components are few, prices are high, and the feedback on long-term reliability is nonexistent. On top of all this is the elephant in the room: the unexplored safety ramifications that accompany high-voltage DC.

However, none of this should deter the dedicated tinkerer who has funds to match his curiosity and who can live within the parameters imposed by electric propulsion.

Practical Sailor encourages our readers to explore the technology, because ultimately, it is the experimenters who bring us the equipment we eventually come to take for granted.

• Pricing Electric Power for a 30-foot Sailboat
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I have gotten excited about repowering my Freedom 30 with an electric motor. A fellow Freedom 30 owner completed his refit about 8 months ago and is very happy with the result, although he wishes he had gone with larger Lipo batteries. He chose a motor from electricyacht.com which sells a 10KW package (quietTorque 10) including motor, performance display, throttle and shaft coupler for $6K. Batteries and charger are extra. The motor does does feature a regen capability. Figure a $10K investment. Big bucks for sure but equivalent to a yard installed diesel repower. I would do the install myself.

I am not a cruiser but have done some lengthy passages from San Francisco to Hawaii. Ideal conditions for regen. I expec between regen and a hundred watts of solar, I could have kept the bank topped up the whole way down despite AP loads, etc. The way back? Not so much. Realistically you would need a small generator and a good stock of gas if you wanted to do much motoring, Having said that, one of the boats that sailed down there with me came home with an outboard as his aux power. I think he had ten gallons of gas.

But I am not planning ocean passages in future, I will be sailing the SF Bay and coastal cruising. When I think about eliminating the engine noise, engine maintenance, fuel tank and tank maintenance, diesel hoses, diesel smell, diesel soot, diesel leaks, r=two boxes of hoses and spares. oil changes, coolant changes, transport and disposal of all the waste to the local recycling facility, lugging fuel jugs down to the boat, storing fuel, filling fuel, buying fuel, worrying about spilling fuel. I mean it just goes on and on.

Frankly, I can’t wait. In terms of range, well, I plan to get a hefty battery bank but I also intend to become a better sailor. I’ll slow down and do more sailing. Gee wiz, what a concept. I’ll be more mindful of time and tide, I’ll take advantage of favorable currents and I’ll be ready to anchor and chill when they are not favorable.

Meanwhile, Elon and his competitors are improving battery technology rapidly. Couple of years from now maybe I double range. But, by then, I won’t be worrying about it because I will be a real sailor.

I look forward to reading an update on the state of electric sailboat propulsion 13 years later…

Most of the time we leave the dock, motor for under half a nautical mile to get out of tiny Wilmette harbor and get the sails up, turn off our much abused Yanmar 3GMF, sail around, turn on the engine, lower the sails, and travel another half a nautical mile back to the dock. Almost all at a very low RPM. But, on occasion we motor or motor sail long distances for hours on end, so a battery only system would not work. But how nice it would be if we had electric propulsion for getting in and out of the harbor.

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Over 100 years after the first (successful) diesel-electric yacht, Southern Wind explain how hybrid marine power is taking a big step forward in a size range that allows better use of industrial developments in other sectors.

What will the next superyacht launched by Southern Wind Shipyard have in common with more than 400 New York City buses? Absolutely nothing, until you look in the engine room where you’ll find the same diesel-electric power and propulsion technology from BAE Systems. The  SW96#04 , due for delivery next summer, is Southern Wind’s first yacht with a hybrid drive, a major milestone for the shipyard. And their next diesel-electric project is already taking shape: the brand new  SW108 Hybrid  which has already been sold for delivery winter 2023. If the current level of interest from clients is sustained, Southern Wind expects to be building up to – two hybrid-powered yachts per year going forward.

It might seem strange to source a hybrid drive from the public transport industry rather than using a system designed from the outset specifically for marine use, but it actually makes a lot of sense. Most if not all of the commercial marine diesel-electric hybrid systems currently on the market are far too big for a 29-metre (96ft) sailing yacht and the leisure marine systems are much too small. The suppliers at both ends of the spectrum don’t see enough demand to upscale or downsize their existing products, so there’s a gap in the middle of the market from around 200 to 400kW (roughly 300 to 500hp). Or rather, there was a gap which BAE Systems has now filled, in partnership with Southern Wind.

There’s also the key issue of reliability. Diesel-electric marine propulsion has been around for more than a century, going all the way back to Jack Delmar-Morgan’s motor yacht Mansura in 1912, but none of the current marine-specific hybrid drives are anywhere near the maturity of BAE Systems’ technology, which has been deployed in more than 14,000 vehicles worldwide over the last 25 years. It’s proven beyond doubt to be extremely reliable with complete dual redundancy built in, and it’s backed up by a global support network of skilled technicians who already have years of repair, maintenance and troubleshooting experience.

BAE Systems’ hybrid expertise goes far beyond buses – it’s also the leading supplier in many aerospace and commercial applications, including ferries and offshore fishing vessels. It’s a smart move for Southern Wind to tap into this huge infrastructure and economy of scale.

What are the benefits of hybrid propulsion? Apart from the fuel economy gain of a system that always runs at peak efficiency – conservatively estimated between five and 30 per cent for a Southern Wind hybrid – and the resulting reduction in carbon footprint, there are four major advantages for a sailing boat and especially for a long-range ocean cruiser that needs to operate in complete autonomy for weeks or months at a time.

First, there’s the ability to regenerate power via the propeller and keep the yacht’s batteries charged for the whole duration of an ocean passage under sail, running the sailing systems and some hotel systems without using any fuel. ‘When you’re crossing the Pacific for example it means that you can arrive with full tanks in a remote area like the Marquesas or Tuamotus and start exploring the small archipelagos immediately, without first having to go and refuel,’ Micheli says.

Second, the hybrid system’s huge battery capacity enables a yacht to operate for periods of time in silent mode with zero emissions, under power and at anchor. There’s no need to run generators overnight in an anchorage, which improves the quality of life for people on other yachts nearby as well as for the owner and guests on board. Silent running also means zero pollution, less disturbance to wildlife and a better experience for guests in wilderness areas and conservation zones.

Third, a hybrid system powered by two relatively small generators instead of one big engine allows a large yacht to circumvent the stringent IMO Tier 3 regulations for all new marine diesel engines with a power output greater than 130kW (174hp). Exclusion zones for noncompliant vessels already exist in the US and are due to be enforced in the North Sea, with other areas expected to follow. The nitrogen oxide (NOx) reduction requirements of Tier 3 are a challenge for yacht builders, Micheli says, because the solutions that have been developed for commercial shipping such as selective catalytic reduction (SCR) are impractical for a sailing yacht with a 300-450hp auxiliary engine.

The fourth big benefit of hybrid drives is their longevity. In a conventional installation, a yacht’s gensets are typically replaced (or completely rebuilt) after 20,000 hours and the engine after about 25,000 hours. By contrast, as Southern Wind’s technical manager Yann Dabbadie explains, the BAE Systems HybridGen drive is rated for 52,000 hours of running.

Crews and owners aren’t very comfortable with the technology, Micheli says, because they don’t fully understand it Hybrid drives do require high-voltage power that is potentially lethal but in the Southern Wind/BAE HybridGen setup it’s safely confined to sealed units within the engine room. It doesn’t run all around the boat. ‘The architecture of the system is optimised for safety as well as weight, performance and reliability,’ Dabbadie says. ‘There are no loose terminals and all junction boxes are protected. Even if you accidentally opened a junction box, there is no way you can hurt yourself as the system will cut the high voltage automatically. The system is built to class requirements, it’s installed on ships already and we’re working closely with RINA.’

Another reason for the slow uptake of hybrid drives, especially for racing yachts and high-performance cruisers, is that they usually weigh more and take up more space than a conventional engine – but this one doesn’t. ‘It’s about a ton lighter than any of the other hybrid systems on the market,’ Dabbadie says. ‘The total weight depends on the battery capacity that the owner chooses to have but if you compare like for like it’s not much heavier than a normal diesel installation.’ It also occupies the same amount of space, and fits neatly into the existing engine rooms of most yachts that Southern Wind has built, so it’s a viable retrofit option for many owners.

Yacht owners and crews are also quite often sceptical about the availability of technical support and troubleshooting services when they’re anchored off a remote island or sailing in mid-ocean, thousands of miles from land. Once again Southern Wind has a solution, drawn this time from the offshore power industry. Crews receive training from BAE Systems as part of the yacht’s sea trials and a headset with a camera and virtual reality visor could possibly be supplied for remote assistance. A low-bandwidth satcom link is all that’s needed to provide expert guidance and to troubleshoot any problems remotely. For servicing or maintenance work in far-flung parts of the world, a local technician can be sent from the nearest service centre.

All of this, however, is just one part of a wider drive towards more sustainable yachting at Southern Wind. The efficiency gains of a new, remarkably efficient air conditioning system are expected to be even more significant for a yacht in typical charter usage than the benefits delivered by the HybridGen propulsion system. And that’s just the start of a new direction for this innovative shipyard.

• Hybrid marine power
• Southern Wind

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Yanmar’s Electric Propulsion Systems

Yanmar Offers a New Direction for Marine Power

Electric propulsion systems utilize electrical power to drive propeller blades for propulsion. From commercial and research ships through to fishing vessels, over recent years, electric propulsion has gained momentum in a wide range of marine applications across Europe and in Japan. Our power system offers improved economic and environmental performance, with robust reliability and reduced life cycle costs, with consideration for the environment. At Yanmar we handle all areas relating to the electric propulsion system from engine design and manufacture to making hull design improvements.

Electric Propulsion System Overview

A propulsion system that outrivals conventional propulsion engines in efficiency and functionality.

In conventional power system arrangements, the ship’s propellers are driven by a diesel propulsion engine while the supply of electricity for the other shipboard loads is transmitted via the shipboard generators. In electric propulsion systems, the power used to drive the propellers becomes an electrical load meaning that the generators can take care of all shipboard loads. As shown in the diagram below, 3 generator-drive engines are referred to as the "ship’s electric power station" supplying power for both propulsion and electrical requirements on board.

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How to convert a yacht to electric propulsion

• Duncan Kent
• May 22, 2024

Thinking about changing your ageing diesel engine for a new all-electric propulsion system? Duncan Kent offers advice on the pros and cons

There are hundreds, if not thousands of yachts still sailing with 40-year-old diesel engines emitting smoke and pollutants, so is now the time to replace them with a clean, low maintenance, pure electric propulsion instead?

The more I’ve looked at sailing yachts that have been converted from diesel to electric auxiliary drive, the more I wonder why you wouldn’t do it, especially now that the cost of hi-tech boat batteries and solar charging has dropped dramatically.

The immediate advantage of changing to marine pure electric drive (PED) systems is that they’re clean, quiet, smell-free and require minimal maintenance, all of which is very appealing if you’ve ever owned a boat with an ancient, clunky diesel. PEDs offer other benefits too. Their reaction to the throttle is instant, which is a boon when berthing in a cramped marina, and once you’re sailing at a decent lick you can generate free ‘fuel’ from the prop.

The disadvantages are the initial cost of the system (largely due to the batteries) and range issues. On a typical 10m cruising yacht it’s just not possible to store enough energy to motor at full tilt for 10 hours a day, so if you’re planning to make long offshore passages regularly then you’ll either need a lot of patience or enough solar and wind generation to power a small village.

But for coastal cruising, often from marina berth to marina berth (what 85% of today’s boat owners do anyway), a PED system is far more viable, especially once your old iron topsail has reached the point where it’s just so much ballast.

If there’s even a little bit of you that would rather not get your hands dirty tinkering with a temperamental diesel, then electric may just be for you. Photo: Fernhurst Books

The devil you know

A diesel engine can provide heaps of grunt when you mistime the tides and want to escape an oncoming storm, provided, of course, that choppy seas haven’t stirred up the inevitable gloop at the bottom of your diesel tank and blocked up your fuel filters.

It’s also fairly simple tech, so, if you’re mechanically minded and have all the tools and spares on board, you can usually keep it turning over. Fuel can also be carried in jerries too, so if it takes a bit longer to thrash your way back into port you can top it up along the way.

You can also leave the boat for months, even years, on end without much harm coming to it and without needing an umbilical cord permanently attached to the shore to keep the expensive power pack in optimum condition.

A spare charged battery, a pair of jump leads, some fresh fuel and bingo, you’re away. But if there’s just a little bit of you that would love to never have to lift the engine box lid and prefer to start your annual cruise with clean fingernails, then sliding soundlessly out of your berth in the early hours must sound appealing.

Range currently remains an issue with battery capacity the limiting factor, but things are improving all the time

Range anxiety

Just as with electric cars, whenever anyone whose vessel is equipped with a conventional diesel falls into a conversation about electric propulsion for boats, the first question is almost always, ‘How far will it go on a charge?’

Well, the answer I’m afraid is simply, ‘It depends.’ How far do you want it to go? Are you willing to toddle along at four knots, or do you want to charge around from port to port like a Greek charter yacht?

I get that it’s not for everyone and, being a mature seafarer myself, I dread to think about losing all power whilst halfway through the Portland Race in the dark. But as with pretty much anything to do with navigating a vessel, you just need to plan things out carefully in advance.

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There are those that say having a finite source of auxiliary propulsion teaches you to sail better, which in many ways is true. The introduction of the powerful modern marine engine has made us all lazy with our tidal planning, knowing, as we do, that you can always resort to the donk to get you home if the log drops below 4 knots or that extra pint in the pub has made you late for the tidal gate.

So, let’s look at some facts. The typical electric propulsion system for a 10m, 6-tonne cruising yacht will usually be designed to provide around five to six hours of gentle cruising in fairly neutral currents at around 4 knots, or maybe 10 hours of motor-sailing, before requiring a charge.

Unlike a car, however, a boat can have solar panels on its deck, coachroof and arch, that can extend this range by another couple of hours, maybe, in the summer.

And then there’s the possibility of regeneration.

Oceanvolt electric ServoProp propeller has electrically controlled pitch which auto adjusts for your speed, or for regeneration

Hydro-regeneration

Nearly all electric motors used in marine propulsion have the capability to turn into a hydro-generator when your speed under sail goes above 4.5 knots or so and the prop/motor is allowed to rotate in reverse.

Regeneration doesn’t make a massive contribution, at best around 750W at 7 knots boat speed per prop, but at 48V (typical electric drive voltage) that’s another useful 15A or so going back into the battery bank.

There are some systems – Oceanvolt’s ServoProp for instance – that incorporate a variable pitch prop. These are capable of a more decent output at lower speeds but are currently seriously expensive.

Either way, I believe solar and hydro-regen should be treated as a bonus when planning your system, not as a given.

If you are unlucky enough to have a few days of no sun or wind you will be back to relying solely on the energy reserves held in your battery bank.

For those who really can’t get over the nagging worry of running out of drive power on a passage, there’s always the option of installing a hybrid system, in which a standby diesel engine is always on hand to get you out of an emergency.

Oceanvolt’s award-winning HighPower ServoProp 25 electric saildrive

Variable pitch props

A normal fixed propeller is designed for propelling the boat and not for generating power as with a hydro-generator. However, Oceanvolt’s DAME award-winning ServoProp saildrive, suitable for monohulls and multihulls from 35-90ft LOA, features a variable pitch prop that combines a high efficiency saildrive with a powerful hydro-generator.

With its unique ability to rotate its propeller blades through more than 180°, ServoProp’s control software adjusts the pitch of the propeller blades to automatically optimise all hydro-generation and propulsion needs.

Oceanvolt claims that a normal fixed propeller generates less than half the power of ServoProp, which it states can produce more than 1kW at 6-8 knots, and 5kW at 10 knots.

It also estimates a 30% increase in forward propulsion, +100% in reverse, and +300% in hydro-generation mode.

Renowned marine propeller supplier, Bruntons, has also launched its Autoprop Eco*Star, designed specifically to propel the rapidly growing number of hybrid and pure electric craft, both motor and sail.

Autoprops are highly efficient because of their ability to auto-pitch depending on engine speed and sea conditions, in order to provide optimum thrust at all times. But with electric propulsion the advantages provided by the new Eco*Star propellers are further extended.

Electric motors provide a constant torque from zero to maximum rpm. Using its auto-pitching ability, the Eco*Star can match its own efficiency curve with that of the electric motor, resulting in more boat speed with less energy.

Eco*Star can spin when under sail allowing the motor to become a generator for recharging the batteries.

Battery setup in an Oceanvolt electric propulsion unit

Drive types

Shaft drive – In most cases it’s possible to retain the shaft and stern gland from an existing shaft drive ICE system, although you’ll probably need a new shaft bearing and coupler unless it is a direct-drive system. The propeller will also probably need to be changed if you want regeneration when sailing.

Saildrive – In many ways electric saildrive units are easier than shaft drives because, as with pods, they come as a complete package with the correct propeller for optimum regeneration. They’re also more efficient at regeneration as the propshaft can be aligned horizontally, unlike shafts, which are usually angled slightly downwards. Some owners choose to convert from a shaft to a saildrive for this reason.

Pod drive – Electric drive pods are similar to saildrives, except they have a direct-drive motor at the bottom of the leg, which allows them to benefit from automatic cooling. Electric drive pods also only require a few small holes in the hull, usually two to four for mounting the unit and one for the routing of the power cable. Pod props and motors are also designed with optimum regeneration in mind.

Most PED systems on small to medium-sized yachts utilise a 48V battery bank. Although there are some that still use deep-cycle AGM battery technology, the only realistic battery chemistry currently available for marine PED systems is lithium-ion.

The safest of the li-ion group is lithium iron phosphate (LiFePO4). While not the most energy dense of the lithium-ion group, they have been proven to be the safest type of li-ion cells to install into a boat, where a battery fire would be catastrophic.

Originally, many professionally built and installed marine electric drive systems utilised other, more volatile types of li-ion batteries such as nickel manganese cobalt (NMC) or lithium manganese oxide (LMO).

System displays can give real time readouts of battery capacity, power usage and remaining range

These types of li-ion are commonly used in the automotive industry for their high capacity, but are wholly reliant on their highly sophisticated battery management system (BMS) to keep them operating within safe parameters.

Apart from preventing a fire risk, the problem with relying on a BMS to monitor the batteries is what happens if something triggers a safety shutdown, causing your boat to lose power completely. A battery shutdown isn’t as drastic as having a lithium battery fire on board, but the total loss of propulsion isn’t ideal, even on a sailing boat.

It’s worse, of course, if you use the same power bank for your house power. Then the loss of your navigation and communications facilities at the same time can be extremely dangerous. For this reason, I would always recommend keeping motor and house banks entirely separate from each other.

If you’re happy to have the more volatile batteries on board or are forced to in order to achieve the desired range, then I highly recommend you have your system professionally designed, installed and commissioned.

Yes, it’ll be expensive, but you’ll sleep at night!

The battery monitoring system will control charge from all sources

Charging a motor bank

Having a much lower internal resistance, li-ion batteries will charge more rapidly than lead-acid batteries because they can accept a much higher rate of charge.

A good quality battery can usually accept a charge up to its own capacity, meaning a 100Ah battery can be charged at 100A. This is called a capacity acceptance rate (CAR) of 1C, and is important when it comes to charging overnight, with the intention of continuing your cruise early the next day.

It also enables various different methods of charging to be accepted simultaneously, provided the combined charge doesn’t exceed 1C, so you can be using solar to its max while also charging from shore power. Another advantage of using li-ion over lead-acid batteries is the BMS can be networked to all charging sources to provide control over the charging regime, plus the data can provide power monitoring at a glance.

Costs of converting

The cost of installing a complete pure electric drive system on a yacht depends on how far and how fast you want to motor between battery charges. The greater the range or faster the speed required, the more battery capacity you’ll need.

A typical 40hp diesel replacement will cost close to £20k including all the parts and installation. A DIY-installed PED replacement would cost £15-£25k, depending on the number of batteries specified, whereas a professionally designed and installed pure electric drive system is more likely to be in the region of £30-£45k.

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Flexible, future-proof choice

Electric marine propulsion – future-proof and flexible

Electric marine propulsion is your flexible, future-proof choice. Flexibility is a must for your propulsion system because so many things in shipping are uncertain. Flexibility safeguards you from the uncertainty about the availability and cost of sustainable fuels, for example. If you are not sure about the additional power sources that will support your combustion engines, you will need flexibility. And you need it also if you do not know exactly which operational profiles will be sailed.

The classical diesel-electric propulsion systems are so flexible because of their one major advantage. The power generating units (gensets) are only electrically connected to the electric propulsion system. This makes it easier to replace the units with a new power source – such as a future-fuel operated engine, a battery, or a fuel cell.

The following is an example configuration of a diesel-electric propulsion system on a vessel:

Diesel-electric propulsion systems continue to be a solid choice for ships that

• have a significant hotel load, such as cruise ships
• need to move with varying speeds, such as offshore and special vessels.

The current decarbonisation requirements mean that many more types of vessels are considering to adopt electric propulsion.

Wärtsilä has delivered electric propulsion systems to more than 350 vessels – to tugs, offshore vessels, research and special vessels, and to large cruise ships.

Benefits from electric marine propulsion systems

Lower emissions.

The electrical propulsion system is and environment-friendly choice – even with diesel generators. This is because the electrical propulsion system makes it possible to operate the generators within their optimal operational range even when the load from propulsion varies. Therefore, adopting electrical propulsion for a ship will significantly reduce the emissions of NOx/NO, CO, CO2, and soot.

At lower propeller speeds, the number of generators that are online can be adjusted according to the power demand. The engines will run more efficiently, which saves fuel.

Low noise and vibration

Electric propulsion drives are unsurpassed for their quietness of operation.

More reliable

The propulsion system on the ship can be configured for better redundancy. This makes the system more reliable.

Responds to operational needs

The torque-speed of the motor makes it possible to high-over torque at propeller standstill. The propeller can be driven at all speeds and torques within design limits – there are no other limitations.

Smoother manoeuvring and positioning

The electric propulsion system has excellent dynamic characteristics. Changes in propeller speed and propeller reversals during manoeuvring and positioning can be carried out at optimum acceleration rates.

Outstanding mains quality

The electric propulsion system generates only minimal harmonics or voltage drops, which means that the interference to mains is also minimal.

Easier to operate

A ship navigation and command system can control the electric propulsion drives automatically, and manually from any control console. The functions and operating states are monitored, which will prevent operating mistakes and overloads.

Leaner installation and OPEX savings

Choosing an electric propulsion system for a ship instead of a diesel mechanical one means that there are fewer diesel motors and cylinders. The system also allows the motors to operate at constant speed, which reduces wear and tear. The result: lower costs of maintenance and less frequent demand for spare parts, which saves money.

Are there any disadvantages?

Marine electric propulsion does have one drawback when compared to mechanical propulsion: electric losses. However, the losses are usually smaller than people think, and this article explains why the high losses are a myth .

Even so, electric propulsion is a superior choice because it is so flexible. After all, you can change the type of the propulsion power source, and the rest of the propulsion system can remain as it is.

Converter topologies

There are three basic topologies for an electric marine propulsion system: AC system, DC system, and Wärtsilä’s patented Low Loss Solution. Wärtsilä will consider your vessel’s needs and propose the optimal topology, which may be a smart combination of the basic topologies.

Alternating Current (AC) systems are the most common diesel-electric propulsion solution, in Low Voltage (440 / 690V) or Medium Voltage (6.6 / 11 kV) settings. AC systems combine a switchboard with transformers and AFE (Active Front End) or DFE (Diode Front End) converters for each propulsor.

The Direct Current (DC) system is gaining popularity. A DC system is always in Low Voltage (1000V) setting. It has the advantage that it can connect variable speed gensets and batteries (which are always DC).

A DC Hub is a combined DC switchboard with converter modules. It is not always smaller or more light weight than the AC equivalent. It is important to weigh the possible advantages of a DC system, especially for a hybrid propulsion system.

Learn more from the article  “DC or not DC, that is the question” .

Low Loss Solution

The patented Low Loss Solution from Wärtsilä reduces the number of transformers needed and reduces the electric losses. At the same time, it increases the redundancy of the propulsion system.

With its 200+ installations, the Low Loss Solution is the market standard for DP (Dynamic Positioning) / offshore vessels. 

Electric propulsion for merchant vessels

An electric propulsion system is the ideal choice for owners who feel uncertain about the future of propulsion solutions. The benefits become even more attractive when the vessel will be operating at varying speeds and have a high hotel load. Merchant vessels such as feeders, RoRos, short-sea PCTCs (pure car and truck carriers), and small tankers will gain significant benefits from an electric propulsion system.

Electric propulsion for cruise ships and ferries

Most modern cruise liners and ferries are designed with diesel-electric propulsion systems. These offer numerous advantages in terms of low noise and vibration-free operation, maximized cabin related loading capacity, more economic operation - especially the improved efficiency in partial propulsion power mode, a high degree of reliability, availability and redundancy, lower emission levels, and reduced wear and tear.

Electric propulsion for large LNG carriers

Electric propulsion can make it possible for LNG carriers to enter a new era of decarbonisation – and increase their cargo capacity at the same time. The next generation hybrid electric LNG carrier design features an impressive 185kcbm cargo capacity within the standard dimensions and displacement of a 174kcbm vessel design. The design is the result of broad industry collaboration. Its five Wärtsilä 31 Spark Gas and Dual Fuel generating sets offer best efficiency and lowest emissions in this segment.

Electric propulsion for offshore vessels

Offshore vessels, pipe and cable laying vessels, and heavy lift jack-up vessels have a long operations time at zero or slow speed and they are often required to change their speed rapidly. Therefore, they need a propulsion system with excellent dynamic characteristics to support their manoeuvring and positioning moves and reversals.

Electric propulsion for special vessels

The ideal propulsion system for special vessels is based on speed-controlled DC or AC motors which drive the propeller either directly or via gears. Research and survey ships and fishery supervision vessels often choose the direct drive option because it is the most reliable and low noise design. Multi-purpose vessels and icebreakers require propulsion systems with excellent dynamics to permit the flexible use of the torque speed characteristic, up to high-over torques and propeller standstill.

Electric propulsion in ships - examples

Discover the benefits others have already gained. Marine electric propulsion systems in offshore vessels, cruise ships, tankers, ferries, research vessels, tugs, yachts.

When Silversea’s luxury cruise liner Silver Dawn needed a high-quality, reliable and quiet propulsion system, Fincantieri shipyard turned to Wärtsilä.

Princess Cruises relies on Wärtsilä’s propulsion system for minimal engine noise and vibrations and ultra-reliable operation on its vessel Discovery Princess.

Wärtsilä Hybrid upgrade brings significant fuel savings for offshore vessel

A broad range of solutions for a new tanker class that reduces not only the environmental impact from the vessel itself but from the cargo too.

Wärtsilä has worked closely with the owner to develop a customised integrated solution based on the ship’s operating profile and customer-specific requirements. Reliability, efficiency, and low operating costs were key considerations.

Wärtsilä provides ultra-silent propulsion technology for Faroese research vessel Jákup Sverri

Wärtsilä will provide and integrate the electrical system package for a new German research vessel Meteor IV

Related solutions

Interesting insights

Discover these hand-picked articles to learn more about electric propulsion for ships.

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Find the right engine for diesel-electric propulsion

Full range of man four-stroke engines for diesel-electric propulsion.

Explore the capabilities and range of our engines.

Powerful and strong: Our four-stroke engines for diesel-electric propulsion

Man l+v51/60df (de).

MAN Energy Solutions integrated its in-house core technologies to create the dual fuel marine MAN L+V51/60DF engine that converts liquid fuel, natural gas or a combination of both into electric or mechanical propulsion power.

• High-efficient variant/high-power variant 500 – 514 rpm/500 – 514 rpm
• 6,300 – 16,800 kW/6,900 – 16,100 kW

MAN L+V49/60DF (DE)

The MAN 49/60DF is future-proof in multiple ways. Its benchmark fuel efficiency guarantees competitive vessel operation. The very low level of methane emissions ensures long-term CO2 emission compliance.

• 7,800 – 18,200kW
• At 600 rpm: 1,300kW
• Power-to-weight ratio: 13.5 – 16.7 kg/kW
• Gas mode: 6,990 kJ/kWh

MAN L+V48/60CR (DE)

The MAN L+V48/60CR injection system uses the latest MAN Energy Solutions common rail technology, allowing for flexible setting of injection timing, duration, and pressure for each cylinder.

• 500 – 514 rpm
• 7,200 –19,200 kW

MAN L35/44DF (DE)

The MAN L35/44DF offers high output, dual fuel flexibility, and Tier II and Tier III compliance. It is ideal for mechanical propulsion, electric propulsion as well as auxiliary GenSet applications

• 720 – 750 rpm
• 3,060 – 5,300 kW
• 2,953 – 5,115 kWe

MAN L+V32/40 (DE)

The MAN L+V32/40 range runs on inexpensive HFO from standby to full load. Twin camshafts provide unsurpassed flexibility, permitting a wide range of choices between optimal output/fuel ratio and minimized emissions.

• 720 – 750 rpm
• 3,000 – 9,000 kw
• 2,895 – 8,730 kWe

MAN L+V32/44CR (DE)

By employing the latest technology combined with electronically controlled common rail injection, the MAN L+V32/44CR is setting new benchmarks in its class, such as low NOx, CO2, and soot emissions

• 3,600 – 12,000 kW
• 3,474 – 11,640 kWe

The LNG-fueled MAN L28/32DF is based on the proven and classic design of the MAN L28/32 H. It is characterized as highly reliable and robust engine with long TBOs.

It is applicable for both, new buildings and retrofits. As a dual fuel engine, it offers fuel flexibility while being efficient and emissions-compliant in both  modes.

• 1,050 – 1,890 kW
• 1,000 – 1,800 kWe

MAN L27/38 (DE)

The MAN L27/38 GenSet is designed for lifelong operational reliability and ensures trouble-free operation and long and safe overhaul intervals. It will be ready and running when you need it.

• 720 – 750 rpm
• 1,500 – 3,150 kW
• 1,440 – 3,025 kWe

MAN L27/38 Mk2 (DE)

MAN L27/38 Mk2 units offer reliable operation. They can run on conventional fuel types and biofuels and deliver low OPEX during their entire life cycle.

• 720 – 900 rpm
• 1,980 – 3,690 kW
• 1,900 – 3,540 kWe

MAN L23/30H Mk2 (DE)

The MAN L23/23H is a workhorse which was first introduced in the mid-60s. Since then, it has proven to be an outstandingly reliable engine type and in effect benchmark for the marine industry.

It comes with a proven track record of more than 12,000 units installed. 

• 720 – 900 rpm
• 580 – 1,400 kW
• 550 – 1,330 kWe

The MAN L23/30DF is part of the small-bore dual-fuel engine range. It’s design features support fuel flexibility in line with compliance to all emissions regulations.

This combination makes it an ideal choice for newbuilding projects, and also as retrofit.

• 720 – 900 rpm
• 625 – 1,320 kW
• 590 – 1,255 kWe

The MAN L21/31 is MAN Energy Solutions’ first small-bore GenSet fueled by methanol. It is a reliable and compact engine which can be operated on methanol, heavy fuel oil (HFO), and additionally most biofuel oils.

It comes with outstanding load-step capabilities and attractive long time between overhauls (TBOs). It is an ideal choice for many different applications, such as offshore, cable laying, CSOV or also methanol bunker vessels.

• 900 – 1,000 rpm
• 1,000 – 1,980 kW
• 950 – 1,880 kWe

MAN L21/31 Mk 2 (DE)

MAN L21/31 Mk 2 units are characterized by reliable and HFO-based GenSet power, delivered at the lowest possible accumulated costs during an entire life cycle. As such, the GenSet represents a safe investment.

• 900 – 1,000 rpm
• 950 – 1,880 kWe

Powered by the MAN 175D high-speed engine, our marine GenSets combine reliable power with unprecedented compactness. They can be configured with several options to match the requirements of all marine applications.

• 1,500 – 1,800 rpm
• 1,440  - 3,800 kW
• 1,382 - 3,648 kWe

S.E.M.T. Pielstick PC2.6B (DE)

The proven Pielstick PC2.6B design delivers high power density, low emission levels, and reduced running costs in various diesel-electric propulsion configurations.

• 9,000 – 13,500 kW

S.E.M.T. Pielstick PA6B (DE)

The PA6B with an integrated cooling system for fresh water, lube oil, and fuel oil utilizes a compact design for narrow engine rooms. Designed for extreme robustness, the PA6B is made to ensure safety even in the harshest environments.

• 4,200 – 7,400 kW
• 4,074 – 7,178 kWe

Innovative, powerful, and efficient propulsion

Electric propulsion is not a recent innovation, however it has become the “standard” propulsion solution in many applications, especially when it comes to specialized vessels. High redundancy and reliability of the propulsion plant, improved maneuverability of the ship, and lower fuel oil consumption due to optimized loading of the engines are the key. Diesel-electric systems by MAN Energy Solutions are designed to meet customers’ highest requirements. Times are changing and thanks to new direct current (DC) components and an innovative engine control philosophy, diesel-electric propulsion has evolved, creating a much more compact solution with a range of potential applications.

Always on your side: MAN PrimeServ

MAN PrimeServ provides 24/7 service across the globe. Our range of services includes technical support, consulting and OEM spares, as well as maintenance, repair and comprehensive individualized service plans.

How you benefit:

•  Prompt delivery of high-demand OEM spare parts within 24 hours
• Fast, reliable and competent customer support
• Ongoing training and qualification of operators and maintenance staff
• Diagnosis and troubleshooting with our high-performance online service

Do you want to improve the performance of your business? Looking for more efficiency and power?

Start your engines now and reach out to us today. Our global network of experienced engineers is happy to design the perfect-fit solution for you and your project. 

Continue reading

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FIND YOUR HYBRID SOLUTION THAT MEETS YOUR INDIVIDUAL NEEDS

Hybrid systems for yachts, take your leisure to the next level with quiet, clean and intelligent solutions..

Make the most of your yachting experience with an mtu Hybrid PropulsionPack. Not only does hybrid power reduce on-board noise levels, emissions and vibrations, it also improves efficiency, dynamics and comfort. The components for onboard power and propulsion are modular and scalable. Each hybrid system can be individually designed to meet your requirements.

Enjoy the benefits of silent but highly efficient electric propulsion, exhaust emission-free anchoring – no smell, no smoke, no noise –, emission-free maneuvering in harbor areas, and an all-round environmentally friendly system.

Great maneuverability, E-power assisted propulsion

Comfortable

Silent, vibration-free operation

Meeting the newest emission regulations

Optimized maintenance and operation costs

Discover the mtu Hybrid PropulsionPack

SERIES 2000

Power Distribution Unit

mtu engine series 2000

Electric Machine

BatteryPack

SERIES 4000

mtu engines series 4000

Combining full performance with eco-friendly sustainability: ​Hybrid propulsion opens up a new generation of yachting experience

Discover the future for yacht propulsion in our use case - as  flexible and sustainable as never before, with the same power

Use case Yacht hybrid propulsion

Hybrid  solutions  are  among  the  keystones  of  a  sustainable  future. The power of a diesel engine, which allows top speeds, is combined with the sustainable, emission-and vibration-free comfort of an electric drive. The highlight, in addition to fuel and cost savings, is that with a hybrid system, yacht owners can explore waters previously off-limits to diesel drives with a clear conscience. The following use case shows you what such a journey might look like. Learn more in the use case about:

• How comfort and sustainability are strengthened by a hybrid system
• What flexibility hybrid systems allow on board
• How hybrid propulsion systems enable journeys into unique waters

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The driving force behind safe, efficient and sustainable operations

Azipod® electric propulsion

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News and highlights

ABB introduces CO2e Calculator for enhanced transparency on emissions in vessel operations

The CO2e Calculator allows shipowners to estimate the reductions in carbon dioxide-equivalent emissions enabled by ABB solutions

ABB and Carnival Corporation sign strategic partnership for Azipod® propulsion services

Long-term partnership agreement covers service for vessels powered by Azipod® XO electric propulsion system

ABB to supply ice-classed Azipod® propulsion for new polar research vessel

ABB has won an order to deliver compact Azipod® DI propulsion system to the new polar research icebreaker of Chinese Institute of Deep-sea Science and Engineering

Aeolus collaboration offers a compelling path to future-proof yachting

Designed to stand the test of changing attitudes to the environment and lifestyle at sea, the unique superyacht concept Aeolus is a multidisciplinary collaboration with power and propulsion technology from ABB at its core.

Azipod® propulsion ticks all the boxes in the growing retrofit market

ABB’s market leading Azipod® electric propulsion system has become a commercially attractive retrofit option for existing vessels as shipowners seek ways to comply with new emissions regulations.

ABB to power two new multi-purpose patrol vessels for Finnish Border Guard

ABB will supply an integrated power and propulsion package comprising dual Azipod® propulsors and the Onboard DC Grid™ power system for two newbuild Finnish Border Guard patrol vessels

ABB’s mid-range Azipod® propulsion to power four cruise vessels built by Fincantieri

Four newbuild vessels will each feature a pair of 7.7 MW Azipod® propulsion units for high efficiency, maneuverability and passenger comfort

ABB and Incat sign LOI to develop lightweight hybrid-electric ferry

In a groundbreaking collaboration between the two companies, the announcement paves the way for ABB to supply zero-emission power and propulsion solutions and evaluate a future commercial arrangement for the 148-meter long ferry and similar vessels.

Recent development of icebreaking ship propulsion

Icebreakers have been sailing for some 120 years. At first only slightly more powerful than ordinary commercial vessels, in the early years icebreaker propulsion systems consisted of steam engines connected to a propeller. Marine diesel engines later began to replace steam engines in tandem with advances in electric equipment technology.

ABB to power two new Ritz-Carlton Yacht Collection vessels with Azipod® electric propulsion

ABB to supply complete propulsion packages for two Ritz-Carlton mega-yachts, further strengthening the collaboration that began in 2017 with the hotel group’s entry into the maritime market.

Making sea traffic more sustainable: ABB technology to power new hybrid-electric ferries

ABB will supply complete power, automation and propulsion solutions for three hybrid-electric passenger and car ferries to operate in the Baltic Sea.

ABB and PONANT enter 10-year MarineCare service agreement for increased vessel safety and uptime

Le Commandant Charcot, which recently became the first exploration cruise ship to reach the geographic North Pole, has signed up for ABB MarineCare services to ensure safe and sustainable operations. 

ABB’s Azipod® propulsion factory in Shanghai marks 10-year anniversary

Over the course of a decade, ABB’s Azipod® propulsion factory in Shanghai, China, has successfully delivered 170 units with a total output of 500 MW.

Key benefits of Azipod® propulsion

Azipod® propulsors for highest ice classes

Proven technology & reliable partner

Proven propulsion technology securing successful icebreaking operation through decades of experience 

Technical reliability

Icebreaking & operational efficiency

Azipod® ICE ( 2-5 MW )

Azipod® ICE propulsion is an azimuthing propulsion solution for wide range of icebreaking vessels for power up to 5 MW. With a built-in high-efficiency LV permanent magnet motor and fixed-pitch propeller mounted directly on the motor shaft, it stands out from other thruster solutions. Azipod®  ICE propulsion is extremely robust propulsion device with the simplicity, strength and reliability for the most challenging ice conditions.

Azipod® VI ( 6-17 MW )

Azipod® VI propulsion is a unique azimuthing solution for ice applications, available in the power range of 6-17MW. With a built-in high-efficiency AC motor and fixed-pitch propeller mounted directly on the motor shaft, it stands out from other thruster solutions. While mechanical thrusters have complex transmission with gears and shafts, the Azipod® propulsion has only electrical cables between the power source and the thruster unit. This makes it possible to build an extremely robust propulsion device with the simplicity, strength and reliability for the most challenging ice conditions, and to any ice class.

Azipod® units ( 7.6-22 MW )

Safety and reliability

Environmentally friendly and high efficiency

Responsible supplier with proven service capability

Azipod® MO ( 7.6 MW-14.5 MW )

Azipod® XO ( 14-22MW )

Azipod® XO is a propulsion solution for high-power open water applications. Azipod® XO is available up to 22 MW unit power and it is an ideal choice for vessels like ferries and cruise ships. Azipod® XO brings energy efficiency, excellent maneuverability and improved passenger comfort.

For fast vessels, a Contra Rotating Propeller concept can be applied, leveraging an Azipod® propulsion unit and shaft line propulsion by replacing the conventional rudder with an Azipod® unit where the propellers face each other.

Azipod® units ( 1-7.5 MW )

Propulsion efficiency 

Product reliability

Maneuverability 

Azipod® DO

Azipod® D for open water is a second-generation compact size Azipod® propulsion series covering power range from 1 MW to 7.5 MW. Azipod® D technology combines best features of the original Azipod® C series and the high-power Azipod® XO series.  Azipod® D is the most efficient azimuthing propulsor in its power range and has excellent course-keeping characteristics. Based on its gearless construction and high performance, Azipod® DO provides cost-efficient, reliable and energy saving operations for cruise, ferry, offshore and special vessels. The high performance of the thruster is achieved by a unique hybrid cooling of the propulsion motor combining a direct cooling to the surrounding sea water and an active air cooling system.  Azipod® D is also available with ice classes up to PC 5.

Azipod® DZ

Azipod® DZ is the newest thruster with a nozzle in the Azipod® portfolio. It is available with up to 7,5 MW power. Based on its gearless and simple construction and high thrust performance, Azipod® DZ provides a cost efficient and reliable underwater mountable solution for DP vessels and other ships that require high thrust. The high performance of the thruster is achieved by a unique hybrid cooling of the propulsion motor combining a direct cooling to the surrounding sea water and an active air cooling system. 

 For main dimension drawings, click the underlined Azipod® propulsion models.  *Consult ABB for higher service speeds

Gain more insight

Azipod® propulsion in questions and answers

What is azipod® propulsion, what vessels types are the azipod® propulsion applicable for.

Azipod® propulsion is available in power ranges from 1MW to 22MW, making it suitable for  smaller crafts , yachts ,  ferries ,  cruise ships ,  cargo carriers  and  icebreakers  capable of independently operating in the harshest conditions. Today, over 25 vessel type rely on the Azipod® technology. Passenger vessels  benefit from the performance provided by 360-degree rotating podded propulsors, high reliability and reduced fuel consumption. Additionally, lower vibration and the flexibility of design allowed by locating propulsion motors outside, rather than inside the hull, prove compelling for passenger vessel owners.

For  vessels serving the offshore and energy industries , Azipod® installation requires considerably less space inside the vessel than competing mechanical systems, yielding greater flexibility to optimize vessel design. In addition, optimized installation of thrusters working with a pulling or pushing propeller increases the hydrodynamic efficiency of the vessel and reduces noise and vibrations. Connecting the propeller directly to the propulsion motor eliminates gears and other auxiliary equipment, meaning reduced maintenance costs and less down time due to faults in these systems

Dry cargo vessel  benefit from Azipod® propulsion in operations where vessel must perform reliably over an extended period at maximum efficiency, and need to be especially maneuverable in shallow waters.  For advanced icebreaking tankers and other  icebreaking ships , Azipod® propulsion is a true game-changer with unparalleled icegoing characteristics and efficiency.

Icegoing ships  powered by Azipod® propulsion can run ahead in open water and astern in heavy ice conditions. This capability allows ships to navigate in ice-covered seas without icebreaker assistance, while keeping higher speeds and consuming less power.

What differentiates Azipod® propulsion from conventional propulsion?

Vessel segments.

Offshore vessels

Icegoing vessels

Passenger vessels

Cargo vessels

Special Purpose Vessels

Short distance shipping

Coast Guard & Navy vessels

Other offerings, shaftline propulsion, contra-rotating propulsion (crp), abb ability™ optime - toe angle optimization for propulsion, electric steering for azipod® propulsion.

Are you curious to know more?

Please submit any questions related to Azipod® propulsion here

Submit your inquiry and we will contact you

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• Hydrogen Fuel Cell
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The US’s first hydrogen-fueled ship is officially ready to set sail

The  Sea Change , a hydrogen-powered catamaran ferry, just got Coast Guard clearance to operate commercially in the Bay Area.

Maritime vessel developer SWITCH Maritime received US Coast Guard approval on Friday to operate its flagship hydrogen ferry, the Sea Change, as a public ferry service.

 “We are immensely grateful for the support from the US Coast Guard and all our partners along the path to completion,” said Pace Ralli, CEO of SWITCH. “This is not the finish line, but just a starting point from which to build many more.”

The Sea Change is equipped with hydrogen fuel cells that power its all-electric motors. These cells allow the vessel to travel up to 300 nautical miles (345 miles) at speeds of up to 15 knots (17 mph) and don’t require shoreside charging infrastructure.

Built and launched at All American Marine shipyard in Bellingham, Washington, the  Sea Change  is a 75-passenger catamaran ferry featuring an integrated hydrogen power system from Zero Emission Industries that has 360 kW of fuel cells from Cummins and 600 kW of electric motor propulsion from BAE Systems.

Following a formal launch event in June, the Sea Change  will be operated in a six-month pilot service by the San Francisco Bay Area Water Emergency Transportation Authority (WETA). It’s funded by a public-private sponsorship that includes the Golden State Warriors and a $3 million grant from the California Air Resources Board.

SWITCH Maritime will put the hydrogen ferry into a more permanent route when the pilot finishes. The company is also developing new designs for larger and faster ferries for San Francisco Bay and other major US and international ferry markets.

Read more: Toyota goes large on hydrogen with new US headquarters

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Michelle Lewis is a writer and editor on Electrek and an editor on DroneDJ, 9to5Mac, and 9to5Google. She lives in White River Junction, Vermont. She has previously worked for Fast Company, the Guardian, News Deeply, Time, and others. Message Michelle on Twitter or at [email protected]. Check out her personal blog.

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